Concrete viscosity modifiers (stabilizers)
Thanks to a specially formulated formulation, concrete mix viscosity modifiers allow concrete to achieve optimum viscosity by providing the right balance between agility and resistance to delamination, the opposite properties that come with the addition of water.
In late 2007, BASF Construction Chemicals introduced a new development, Smart Dynamic ConstructionTM concrete mix technology, designed to upgrade P4 and P5 concrete to a higher grade. Concrete produced in accordance with this technology has all the properties of self-compacting concrete, while the process of its production is no more complicated than that of ordinary concrete.
The new concept meets today's ever-increasing need for more flexible concrete mixes and offers a wide range of benefits:
Economical: thanks to the unique process that takes place in concrete, the binder and fillers with a fraction are saved<0.125mm. Стабильная и высокоподвижная бетонная смесь является практически самовыравнивающейся и при укладке не требует уплотнения. Процесс укладки достаточно прост, чтобы производиться при помощи одного оператора, что экономит до 40% рабочего времени. Кроме того, процесс производства почти так же прост, как и изготовление обычного бетона, поскольку смесь малочувствительна к изменениям водосодержания, которые происходят по причине колебания уровня влажности заполнителей.
Environmental: The low content of cement (less than 380 kg), the production of which is accompanied by the emission of CO2, increases the environmental friendliness of concrete. In addition, due to its high mobility, the concrete completely covers the reinforcement, thus preventing its external corrosion. This characteristic increases the durability of concrete and, as a result, the service life of the reinforced concrete product.
Ergonomic: Due to its self-compacting properties, this type of concrete does not require the use of vibro-compacting, which helps workers avoid noise and health-damaging vibration. In addition, the composition of the concrete mixture provides concrete with low stiffness, increasing its workability.
When a stabilizing additive is added to the concrete mixture, a stable microgel is formed on the surface of the cement particles, which ensures the creation of a "bearing skeleton" in the cement paste and prevents the concrete mixture from delamination. At the same time, the resulting "bearing skeleton" allows the aggregate (sand and crushed stone) to move freely, and thus the workability of the concrete mixture does not change. This technology of self-compacting concrete makes it possible to concrete any structures with dense reinforcement and complex geometric shapes without the use of vibrators. The mixture in the process of laying self-compacts and squeezes out the entrained air.
Materials:
RheoMATRIX 100
High performance viscosity modifier additive (VMA) for poured concrete
Technical description RheoMATRIX 100
MEYCO TCC780
Liquid viscosity modifier to improve the pumpability of concrete (Total Consistency Control system).
Technical description MEYCO TCC780
What is Viscosity?
Viscosity is the resistance of a fluid to flow. When one layer of fluid slides through another layer of the same fluid, there is always some level of resistance between these flows. When the value of this resistance is high, the liquid is considered to have a high viscosity and, as a result, flows in a thick layer, for example, like honey. When the fluid flow resistance is low, the fluid is considered to have a low viscosity and its layer is very thin, such as olive oil.
Because the viscosity of many fluids changes with temperature, it is important to consider that the fluid must have the right viscosity at different temperatures.
Viscosity for engine oil.
Engine oils must lubricate engine components throughout the engine's normal operating temperature range. Low temperatures tend to thicken the flow of engine oil, making it more difficult to pump. If the lubricant is slowly getting to the main parts of the engine, oil starvation will lead to their excessive wear. In addition, thick oil will make it difficult to start a cold engine due to the added resistance.
On the other hand, heat tends to thin the oil film and in extreme cases can reduce the oil's protective capabilities. This can lead to premature wear and mechanical damage to the piston rings and cylinder walls. The trick is finding the right balance of viscosity, oil film thickness and fluidity. Solution viscosity modifiers can achieve this. Viscosity modifiers are polymers specifically designed to help control the viscosity of a lubricant over a specific temperature range. They help the lubricant provide adequate protection and fluidity.
The video will help illustrate three key points of viscosity:
- Thin oil flows faster than thick oil.
- Low temperatures thicken oils and slow down their fluidity compared to higher temperatures.
- An oil viscosity modifier can affect its performance.
Viscosity control by polymers.
Two different engine oils: high performance oil (with modifiers) and low performance oil. Both viscosity grades are SAE 10W-40. The beaker on the left corner shows the viscosity of high performance engine oil at room temperature. The second beaker from the left shows how low performance motor oil can thicken during use. The third beaker shows how high performance oil retains fluidity at -30°C. The beaker at the far right illustrates the reduced fluidity of low performance motor oil at -30°C.
When studying chemistry in school, remember that a polymer is a large molecule that is made up of many repeating subunits known as monomers. Natural polymers such as amber, rubber, silk, wood are part of our everyday life. Man-made polymers first came into general use in the 1930s. Synthetic rubber and nylon stockings :) By 1960, the benefits of adding carbon based polymers, which are often used as viscosity modifiers, were universally recognized.
Throughout this period, Lubrizol has been a leader in polymer chemistry for passenger car and truck engine oils. Today, viscosity modifiers (VMS) are key ingredients in most motor oils. Their role is to assist lubrication, achieve the required viscosity and mainly to positively influence changes in the viscosity of the lubricant when subjected to temperature fluctuations.
Viscosity grades
Simply put, viscosity grade refers to the thickness of the oil film. There are two types of viscosity grade: seasonal and all-weather. Oils such as SAE 30 are designed to provide engine protection at normal operating temperatures, but will not flow at low temperatures.
Multigrade oils usually use viscosity modifiers to achieve greater flexibility. They have an identified viscosity range, such as SAE 10W-30. The "W" indicates that the oil has been tested for use in both cold weather and normal engine operating temperatures.
For a deeper understanding of viscosity grades, it is helpful to use examples. Since multigrade oils are the engine oil standard for most cars and heavy trucks around the world today, we'll start with them.
SAE 5W-30 is an all-season engine oil viscosity grade most widely used in passenger car engines. Operates as SAE 5 in winter and as SAE 30 in summer. The value of 5W (W stands for winter) tells us that the oil is fluid, and the engine will be easier in cold temperatures. The oil flows quickly to all parts of the engine and fuel economy is improved because there is less viscous drag from the oil on the engine.
30 part SAE 5W-30 makes the oil more viscous (thicker film) for high-temperature protection during summer driving, keeping the oil from becoming too thin, preventing metal-to-metal contact inside the engine.
Severe-duty diesel oils currently use higher SAE viscosity grades than passenger car engine oils. The most widely used viscosity grade worldwide is SAE 15W-40, which is more viscous (and film thicker) than SAE 5W-30. Winter (5W vs 15W) and summer (30 and 40). In general, the higher the SAE viscosity grade numbers, the more viscous (thicker film) the oil.
Seasonal oils, such as SAE 30 and 40 grades, do not contain polymers to modify viscosity with temperature changes. The use of a multigrade motor oil containing viscosity modifiers allows the user to have the double benefit of ease of flow and starting while maintaining a high degree of engine protection. In addition, unlike seasonal motor oils, the consumer does not have to worry about switching from a summer grade to a winter grade due to seasonal temperature fluctuations.
polymeric viscosity modifiers.
Types of viscosity modifiers:
Polyisobutylene (PIB) was the predominant VM for motor oil 40 to 50 years ago. PIB is still used in gear oils due to its outstanding wear characteristics. PIBs have been replaced by olefin copolymers (OCPs) in motor oils due to their superior efficiency and performance.
Polymethacrylate (PMA) the polymers contain alkyl side chains that inhibit the formation of paraffin crystals in the oil, providing excellent low temperature properties. PMAs are used in fuel economy motor oils, gear oils and transmissions. As a rule, they have a higher cost than OCP.
Olefin polymers (OCP) have found wide application in motor oils due to their low cost and satisfactory performance. Many OCPs on the market vary in molecular weight and ratio of ethylene to propylene content. OCPs are the main polymer used for viscosity modifiers in motor oils.
Styrene Maleic Anhydride Ester Copolymers (Styrene Esters). The combination of different alkyl groups provides excellent low temperature properties. Typical use cases are: efficient fuels, engine oils for automatic transmissions. As a rule, they have a higher cost than OCP.
Hydrogenated Styrene-Diene Copolymers (SBR) characterize fuel economy benefits, good low temperature properties, and performance superior to most other polymers.
Hydrogenated Radial Polyisoprene polymers polymers have good shear stability. Their low temperature properties are similar to those of OCP.
Viscosity measurement, kinematic viscosity
The lubricant industry has created and improved laboratory tests that can measure viscosity parameters and predict how modified motor oils will perform.
Kinematic viscosity is the most common viscosity measurement used for motor oils and is a measure of fluid flow resistance to gravity. Kinematic viscosity has traditionally been used as a guide in selecting oil viscosity for use at normal operating temperatures. A capillary viscometer measures the flow of a fixed volume of liquid through a small orifice at a controlled temperature.
A high pressure capillary viscometer test that is used to simulate the viscosity of motor oils in crankshaft bearing applications to measure high temperature high shear viscosity (HTHS) levels. HTHS may be related to engine durability under high load and severe service conditions
Rotational viscometers measure the resistance of a fluid to flow using torque on a rotating shaft at a constant speed. Cold Cranking Simulator (CCS). This test measures viscosity at low temperatures to simulate starting an engine at low temperatures. Oils with high CCS viscosity can make it difficult to start the engine.
Another common rotary viscometer test is the Mini-Rotary Viscometer (MRV). This test examines the pump's ability to pump oils after a specified thermal history, which includes warming, slow cooling, and cold soak cycles. MRVs are useful in predicting engine oils that are prone to failure under slow cooling (overnight) field conditions in cold climates.
Motor oil is sometimes evaluated by pour point (ASTM D97) and cloud point (ASTM D2500) measurements. Pour point is the lowest temperature at which movement is observed in the oil when the sample in the glass tube is tilted. Haze is the temperature at which a cloud from the formation of paraffin crystals is first observed. These last two methods are no longer used today and have been replaced by specifications for low temperature pumping and gelatinization index.
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It is claimed that low-viscosity oils provide protection even for forced diesel engines. What are the features of this statement? Let's try to figure it out.
In order for low-viscosity oils to provide sufficient protection for diesel engines of heavy equipment and trucks, it is important to study the shear stability in detail. Isabella Goldmints, Lead Scientist for Friction Modifiers at Infineum, talks about some of the steps being taken to investigate the ability of various multigrade motor oils to maintain their viscosity.
Concerns about environmental and economic issues have given impetus to significant changes in the design of uprated diesel engines, especially in terms of emission control, noise control and power supply. New requirements are putting more stress on lubricants, and modern lubricants are increasingly expected to provide superior engine protection over long drain intervals. Adding to the challenge are the requirements of engine manufacturers (OEMs) to provide lubricants with fuel savings through reduced friction losses. This means that the viscosity of engine oils for heavy equipment and trucks will continue to decrease.
Multigrade oils and viscosity modifiers
The Kurt Orban 90 cycle test has been successfully used to determine the shear stability of oils.
Viscosity improvers (VII) are added to engine oils to increase the viscosity index and provide multigrade oils. Oils containing viscosity modifiers become non-Newtonian fluids. This means that their viscosity depends on the shear rate. Two phenomena are associated with the use of such oils:
- Temporary loss of viscosity at high shear rate - polymers align in the direction of flow, resulting in reversible thinning of the oil.
- Irreversible shear losses where polymers break - resistance to such breakage is a measure of shear stability.
Since their introduction, multigrade oils have been constantly tested to determine the shear stability of both new and existing oils.
For example, to simulate a constant loss of viscosity in forced diesel engines, a test is carried out on an injector stand according to the Kurt Orban method for 90 cycles. This test has been successfully used to determine the shear stability of oils and has been firmly correlated with results from use in 2003 and later engines.
However, boosted diesel engines are changing, exacerbating conditions that cause lubricant viscosity shifts. If we want oils to continue to provide reliable wear protection throughout the entire drain interval, we need to fully understand the processes that take place in the most modern engines.
Engine design needs further testing
To comply with NOx emissions regulations, engine manufacturers first introduced Exhaust Gas Recirculation (EGR) systems. The exhaust gas recirculation (re-supply) system contributes to the accumulation of soot in the crankcase, and in most engines manufactured before 2010, soot contamination of drained oils was 4-6%. This led to the development of API CJ-4 oils that could withstand heavy soot contamination and not exhibit excessive viscosity growth.
However, to meet near-NOx exhaust gas requirements, manufacturers are now equipping modern engines with more sophisticated exhaust aftertreatment systems, including Selective Catalytic Reduction (SCR) systems. This innovative technology delivers more efficient engine performance and greatly reduces soot formation compared to pre-2010 engines, meaning that soot contamination now has negligible effect on oil viscosity.
These changes, along with other significant advances in engine technology, mean that it is now important to explore the potential of commercial viscosity modifier additive packages that are added to modern API CJ-4 oils used in those engines that meet the new emission standards.
At the same time, it is necessary to understand whether the laboratory tests we use to evaluate the performance of lubricants are still effective and correlate well with the actual results of using these materials in modern engines.
One of the most important properties of an oil is its viscosity retention throughout the drain interval, and it is more important than ever to understand the function of a viscosity modifier in multigrade oils. With this in mind, Infenium conducted a series of laboratory and field tests of a viscosity modifier (hereinafter referred to as MV) to investigate in detail the performance of modern lubricants.
Field test of wear protection
The first stage of the research work was the establishment of the performance characteristics of the lubricant when applied in the field. To do this, Infineum conducted a field test of various types of MW for different viscosity oils. Engines used were highly shear-friendly and low-soot engines, typical models found in today's trucks or heavy equipment.
The two most popular types of MF are hydrogenated styrene-butadiene copolymers (HBRs) and olefin copolymers (SPOs). The SAE 15W-40 and 10W-30 viscosity grades used in the test contained these polymers and were formulated from Group II base oils with an API CJ-4 compliant additive package. During the test, the oils were changed at intervals of approximately 56 km, at which time samples were taken, which were tested for a number of parameters. The first was that all oils used retained both kinematic viscosity at 100°C and high temperature high shear viscosity at 150°C (HTHS), regardless of their MW content.
Metal wear products have also been given special attention, as low viscosity oils are used to provide adequate fuel economy, and some manufacturers have raised concerns about the ability of these low viscosity oils to adequately protect against wear. However, during the test, there were no wear issues with either oil sample, as measured by the wear metal content of the used oil - no actual difference between oils with different types of MW or different viscosities.
All of the oils used in the field test were quite effective in protecting against wear throughout the test. Also, during the entire oil change interval, there was a minimal drop in viscosity.
Future PC-11 oils
However, the viscosity of lubricants continues to decline, and it is important to prepare for the next generation of motor oils. In North America, the PC-11 category has been adopted, within which a new “fuel-efficient” sub-category, PC-11 B, is being introduced. The oils corresponding to it in viscosity will be classified as SAE xW-30 with a dynamic viscosity at high temperature (150 ° C) and high speed shear (HTHS) 2.9-3.2 mPa s.
In order to assess the prerequisites for the future appearance of PC-11 oils, several test samples were mixed so that their high temperature viscosity at high shear rate was 3.0-3.1 mPa·s. They passed 90 cycles of the Kurt Orban test and after that their kinematic viscosity (CV 100) and high temperature viscosity at high shear rate (HTHS viscosity at 150°C) were measured. The HTHS-CV relationship for these oils is similar to that observed for oils with high high temperature viscosity at high shear rate. However, since these samples are at the lower end of the SAE viscosity grades, after shearing, their CV100 is more likely to fall below the viscosity grade limit than the HTHS viscosity. This means that when developing PC-11 B oils, it will be more important to keep the KB100 within the viscosity grade limits for kinematic viscosity at 100°C than to keep the HTHS viscosity at 150°C.
The result of such tests shows that viscosity loss can be dependent on the viscosity and type of base oil, lubricant viscosity and polymer concentration. In addition, it is clear that lower viscosity oils have better polymer shear stability even at 90 cycles in the Kurt Orban test.
Comparison of field and bench test results
To confirm the results obtained in the laboratory, Infenium analyzed intermediate samples and samples taken after the 56 km replacement interval in field trials. A comparison of bench and field test data shows that the ASTM method makes it possible to accurately predict polymer shear in the field, even in today's highly accelerated diesel engines.
This study shows that one can be sure that the Kurt Orban bench test over 90 cycles is a good indicator of the viscosity loss and viscosity grade retention that can be expected when oils are used in modern diesel engines.
In our opinion, since lubricants are designed not only to provide protection against wear, but also to reduce fuel consumption, it is important not only to choose a viscosity modifier whose composition and structure will give high shear stability, but also to pay great attention to kinematic viscosity .
How does a viscosity modifier work?
You may have come across a "red oil can" - a motorist's horror story, one of the most likely reasons for its appearance is the irreversible destruction of the viscosity modifier. A smooth decrease in pressure in the engine over the life of the oil also indicates an unplanned destruction of the polymer (MB).
Unfortunately, this does not happen so rarely, due to the fact that all components for creating motor (and not only motor) oil are on the open market, in addition to base oil and an additive package containing ready-made products that meet manufacturers' requirements, you can also find viscosity modifiers on sale.
There is only one problem - the raw material base from which the finished product will be formulated varies greatly in quality, and product stability studies can take many months (sea trials) and significant funds.
No organoleptic analysis, no taste, no color, no smell, will help the consumer to separate a quality product from a low-quality one. The consumer can only trust the manufacturer, and therefore should carefully choose the manufacturer of the base oil and additives. The right technology is not just adding additives, but working on all raw materials.
Chevron does more than just create exclusive base oils. The corporation's specialists also develop unique additive systems, which provide Texaco lubricants with excellent performance properties. The Chevron holding includes its own division for the development and production of additives - this is Chevron Oronite. The research and development activities of the company are concentrated in Ghent (Belgium), where in 1993 a completely new technology center was opened, equipped with the most modern equipment, the laboratories of the center conduct hundreds of thousands of oil analyzes per year to provide quality assurance to the consumer.
Specifically formulated, concrete mix viscosity modifiers allow concrete to achieve optimum viscosity by providing the right balance between agility and resistance to delamination, opposite properties that come with the addition of water.
At the end of 2007, BASF Construction Chemicals introduced a new development, Smart Dynamic Construction TM concrete mix technology, designed to upgrade P4 and P5 concrete to a higher level. Concrete produced in accordance with this technology has all the properties of self-compacting concrete, while the process of its production is no more complicated than that of ordinary concrete.
The new concept meets today's ever-increasing need for more flexible concrete mixes and offers a wide range of benefits:
Economic: due to the unique process occurring in concrete, the binder and fillers with fraction< 0.125 мм. Стабильная и высокоподвижная бетонная смесь является практически самовыравнивающейся и при укладке не требует уплотнения. Процесс укладки достаточно прост, чтобы производиться при помощи одного оператора, что экономит до 40% рабочего времени. Кроме того, процесс производства почти так же прост, как и изготовление обычного бетона, поскольку смесь малочувствительна к изменениям водосодержания, которые происходят по причине колебания уровня влажности заполнителей.
Environmental: The low content of cement (less than 380 kg), the production of which is accompanied by the emission of CO 2, increases the environmental friendliness of concrete. In addition, due to its high mobility, the concrete completely covers the reinforcement, thus preventing its external corrosion. This characteristic increases the durability of concrete and, as a result, the service life of the reinforced concrete product.
Ergonomic: Due to its self-compacting properties, this type of concrete does not require the use of vibration compaction, which helps workers avoid noise and health-damaging vibration. In addition, the composition of the concrete mixture provides concrete with low stiffness, increasing its workability.
When a stabilizing additive is added to the concrete mixture, a stable microgel is formed on the surface of the cement particles, which ensures the creation of a "bearing skeleton" in the cement paste and prevents the concrete mixture from delamination. At the same time, the resulting "bearing skeleton" allows the aggregate (sand and crushed stone) to move freely, and thus the workability of the concrete mixture does not change. This technology of self-compacting concrete makes it possible to concrete any structures with dense reinforcement and complex geometric shapes without the use of vibrators. The mixture in the process of laying self-compacts and squeezes out the entrained air.
Star-shaped polymers that can be used as viscosity index modifiers in oil formulations produced for high performance engines. The star polymers have branches of tetrablock copolymers containing blocks of hydrogenated polyisoprene polybutadiene-polyisoprene with a polystyrene block which provide excellent low temperature performance in lubricating oils, have good thickening performance and can be recovered as polymer chips. The polymer is characterized by a structural formula with at least four blocks of monomers, each of the blocks is characterized by a range of molecular weights, in the structure of the hydrogenated block copolymers there is a polyalkenyl coupling agent. 3 s. and 5 z.p.f-ly, 3 tab.
Technical Field This invention relates to hydrogenated isoprene and butadiene star polymers and to oil compositions containing star polymers. More specifically, this invention relates to oil compositions with excellent low temperature properties and thickening efficiency, and to star polymers with excellent processing characteristics. BACKGROUND OF THE INVENTION With temperature, the viscosity of lubricating oils changes. In general, oils are identified by their viscosity index, which is a function of the oil's viscosity at a given low temperature and a given high temperature. This low temperature and this high temperature have varied over the years, but in any given period of time they are captured by the ASTM test method (ASTM D2270). Currently, the lowest temperature indicated in the test is 40°C and the higher temperature is 100°C. For two motor lubricants with the same kinematic viscosity at 100°C, the one with the lower kinematic viscosity at 40°C will have higher viscosity index. Higher viscosity index oils show less change in kinematic viscosity between 40 and 100°C. In general, viscosity index modifiers that are added to engine oils increase both the viscosity index and kinematic viscosities. The classification system in SAE Standard J300 does not include the use of a viscosity index to classify multigrade oils. However, at one time the standard required certain grades to conform to low temperature viscosities, which would have been extrapolated from kinematic viscosity measurements made at higher temperatures, as it was recognized that the use of oils that were excessively viscous at low temperatures resulted in starting difficulties. engine in cold weather. For this reason, preference was given to universal oils that had high viscosity index values. These oils were characterized by the lowest viscosities extrapolated to low temperatures. Since then, ASTM has developed the Cold Cranking Simulator (CCS), ASTM D5293 (formerly ASTM D2602), a moderately high shear rate viscometer that matches engine cranking speed and engine start at low temperatures. Today, the SAE J300 Standard defines cranking viscosity limits set by the CCS, and no viscosity index is used. For this reason, polymers that improve the viscosity characteristics of lubricating oils are sometimes referred to as viscosity modifiers rather than viscosity index modifiers. Today it is also recognized that cranking viscosity is not sufficient to fully evaluate the low temperature performance of lubricants in engines. The SAE J300 standard also requires that a low shear viscometer called a mini-rotational viscometer (MRV) be used to determine pumping viscosity. This instrument can be used to measure viscosity and gelation, gelation is determined by measuring the yield strength. In this test, before determining the viscosity and yield strength, the oil is slowly cooled over two days to a predetermined temperature. Observation of the yield point in this test leads to an automatic shutdown of the oil supply, while the viscosity for pumping must be below this limit so that in cold weather the engine would certainly not experience an interruption in the supply of oil to the pump. The test is sometimes referred to as the TPI-MRV test, ASTM D4684. There are many substances used in fully formulated multipurpose motor oils. In addition to the main components, which can include paraffinic, naphthenic and even synthetically derived fluids, polymer VI modifier and depressant, there are many additives added to the lubricant that act as antiwear additives, antirust additives, detergents, dispersants and depressant. These lubricant additives are usually mixed in the diluent oil and are generally referred to as a dispersant-inhibitor package or "DI" complex. The general practice in formulating a multigrade oil is to blend until the desired kinematic and cranking viscosity are obtained, which are defined in SAE J300 by the mentioned SAE grade requirements. The DI kit and pour point depressant are mixed with VI modifier oil concentrate and one base stock or two or more base stocks having different viscosity characteristics. For example, for an SAE 10W-30 multipurpose oil, the concentrations of the DI kit and pour point depressant can be kept constant, but the amounts of HVI 100 neutral and HVI 250 neutral or HVI 300 neutral base stocks, together with the amount of VI modifier, can be varied to achieve the desired viscosities. The choice of pour point depressant generally depends on the type of paraffinic precursors in the lubricant base stocks. However, if the viscosity index modifier itself is prone to interact with paraffinic precursors, it may be necessary to add another type of pour point depressant or additional pour point pour point used for the main components to compensate for this interaction. Otherwise, the low temperature rheology will deteriorate and the result will be an oil cut to the TPI-MRV. The use of an additional pour point depressant generally increases the cost of producing a motor lubricant composition. Once a composition is obtained that will have the desired kinematic and cranking viscosities, the viscosity is determined in the TPI-MRV method. Relatively low viscosity for pumping and no yield strength are desirable. In the formulation of multipurpose oils, it is highly desirable to use a VI modifier that does not greatly increase low temperature pumping viscosity or yield strength. This minimizes the risk of an oil composition that could cause an interruption in the pump's supply of oil to the engine, and it allows the oil manufacturer to be more flexible in using other components that increase the pump's viscosity. Viscosity index modifiers have previously been described in US-A-4,116,917, which are hydrogenated star polymers containing hydrogenated polymer branches of conjugated diene copolymers, including polybutadiene obtained from a high degree of 1,4-addition of butadiene. US-A-5460739 describes branched star polymers (EP-EB-EP") as a VI modifier. Such polymers have good thickening characteristics but are difficult to isolate. US-A-5458791 describes star-shaped polymers with branches (EP-S-EP"). Said EP and EP' are hydrogenated polyisoprene blocks, said EB is a hydrogenated polybutadiene block, and S is a polystyrene block. it is advantageous to be able to obtain a polymer with good thickening characteristics and excellent processing characteristics. The present invention provides such a polymer. SUMMARY OF THE INVENTION The present invention provides a star polymer having a structure selected from the group consisting of (S-EP-EB-EP") n -X, (I) (EP-S-EB-EP") n - X, (II) (EP-EB-S-EP") n -X, (III) where EP is the outer hydrogenated polyisoprene block having a number average molecular weight (MW 1) between 6500 and 85000 before hydrogenation; EB is is a hydrogenated polybutadiene block having a number average molecular weight (MW 2) between 1500 and 15000 before hydrogenation and polymerized to at least 85% by 1,4-addition; EP" is an internal hydrogenated polyisoprene block having a number average molecular weight before hydrogenation mass (MW 3) in the range between 1500 and 55000;
S is a polystyrene block having a number average molecular weight (MW s) in the range between 1000 and 4000 if the S block is external (I) and between 2000 and 15000 if the S block is internal (II or III);
where the star polymer structure contains from 3 to 15 wt.% polybutadiene, the ratio of MW 1 /MW 3 is in the range from 0.75:1 to 7.5:1, X is the core of the polyalkenyl coupling agent, and n is the number of branches block copolymers in a star polymer when linked to 2 or more moles of a polyalkenyl coupling agent per mole of living block copolymer molecules. Said star polymers are useful as viscosity index modifiers in oil formulations formulated for high performance engines. Tetrablocks significantly improve the low temperature performance of polymers as viscosity index modifiers. Compared to star polymers having a block ratio of less than 0.75:1 or greater than 7.5:1, they allow for reduced viscosity at low temperatures. Therefore, these polymers can be used with a base oil to provide an oil composition with improved viscosity. Concentrates can also be prepared which will contain at least 75% by weight base oil and 5 to 25% by weight star polymer. Detailed description of the invention
The star polymers of the present invention are readily prepared by the methods described in CA-A-716645 and US-E-27145. However, the star polymers of the present invention have molecular weights and compositions that are not described in the references, and which are chosen as viscosity index modifiers to obtain surprisingly improved low temperature performance. The living polymer molecules are coupled with a polyalkenyl coupling agent such as divinylbenzene, where the mole ratio of divinylbenzene to living polymer molecules is at least 2:1 and preferably at least 3:1. The star polymers are then selectively hydrogenated to a saturation of at least 95% by weight, preferably at least 98% by weight of isoprene and butadiene units. Both the size and location of the styrene blocks are critical to improving performance. The polymers described in this invention increase the viscosity measured in the TPI-MRV test less than polymers that do not have an additional polystyrene block. The use of some of the polymers described in the present invention also produces multipurpose oils with higher viscosity indexes than hydrogenated full polyisoprene star polymers or other hydrogenated poly(styrene/isoprene) block copolymer star polymers. The present invention takes advantage of the prior discovery that cyclone-processable star polymers that impart high high temperature high shear (HTHSR) motor oils are produced by attaching small polystyrene blocks to the star polymers. The prior discovery has shown that polystyrene blocks increase the efficiency of cyclone treatment without gelling oil when the polystyrene block has a number average molecular weight in the range of 3000 to 4000 and is in the outer position as far from the core as possible. In this invention, it has been found that the same advantage is obtained if the polystyrene blocks are in the internal position in the tetrablock copolymer, and in the case of the internal position, the molecular weight of the polystyrene block should not be limited to 4000 maximum. Star polymers that contain hydrogenated polyisoprene branches do not suffer from interactions with paraffinic precursors due to the excess alkyl pendant groups that are present when 1,4-addition, 3,4-addition, or 1,2-addition occurs for isoprene. The star polymers of this invention were designed to have minimal paraffin interaction as with star polymers with hydrogenated all polyisoprene arms, but that better performance than star polymers with all polyisoprene arms would be obtained. To prevent the occurrence of high density, similar to that of polyethylene, near the center of the star-shaped polymer, the hydrogenated butadiene blocks are located away from the core by introducing an internal EP block. It is not known exactly why such a situation would be favorable. as viscosity index modifiers, hydrogenated star polymers are used that have hydrogenated branches containing polybutadiene and polyisoprene blocks, the hydrogenated polyethylene-like segment of one branch will be located further from its adjacent neighbors in solution, and the interaction of the paraffin precursor with several hydrogenated polybutadiene blocks of the same polymer molecule On the other hand, polyethylene-like hydrogenated polybutadiene blocks cannot be located too close to the outer edge or periphery of the star molecule.While paraffin-polyethylene interaction should be minimized, placing hydrogenated polybutadiene blocks too close to the outer region star-shaped molecule will cause intermolecular crystallization of these branches in solution. There is an increase in viscosity and possible gelation, which occurs as a result of the three-dimensional crystallization of many star-shaped molecules with the formation of a crystal lattice structure. For intramolecular association to predominate, external blocks (S-EP) (see I), external blocks EP-S (II) or external blocks EP (as in III) are required. To achieve the two goals of minimizing both intermolecular crystallization and interaction with paraffin, the molecular weight ratio EP/EP" (MW 1 /MW 3) should be in the range from 0.75:1 to 7.5:1. The crystallization temperature of these of hydrogenated star polymers in oil can be lowered by reducing the molecular weight of the hydrogenated polybutadiene block along with placing the hydrogenated polybutadiene between the hydrogenated polyisoprene segments and by replacing the EB blocks with S blocks. This decrease in the EB value results in improved TPI-MRV low temperature test results. This also provides the added benefit of butadiene-containing star polymers, which are less sensitive to the type or concentration of pour point depressant and which do not result in oils with time dependent viscosity indexes. Thus, the invention describes viscosity index modifiers that are semi-crystalline star polymers that provide outstanding low temperature performance and that do so without the use of relatively high concentrations of pour point pour point or without the need for additional pour point pour points. The star polymers of this invention, which will be useful as VI modifiers, are preferably prepared by the anionic polymerization of isoprene in the presence of sec-butyllithium, the addition of butadiene to the living polyisopropyllithium after polymerization of the outer block is completed, the addition of isoprene to the polymerized living block copolymer, the addition of styrene at the desired time depending on from the desired location of the polystyrene block and thereafter linking the living block copolymer molecules with a polyalkenyl binder to form a star polymer followed by hydrogenation. It is important to maintain a high degree of 1,4-addition throughout the polymerization of the butadiene block of the block copolymer so that polyethylene-like blocks of sufficient molecular weight are also obtained. However, obtaining an internal polyisoprene block with a high degree of 1,4-addition of isoprene is not of great importance. Thus, after reaching a sufficient molecular weight of the polymer with a high degree of 1,4-butadiene addition, it would be advisable to add a disordering agent such as diethyl ether. The disordering agent could be added after the completion of the butadiene polymerization and before adding more isoprene to form the second polyisoprene block. Alternatively, the disordering agent could be added before polymerization of the butadiene block is completed and simultaneously with the introduction of isoprene. The star polymers of the present invention, prior to hydrogenation, could be characterized as having a dense center or core of a crosslinked poly (polyalkenyl coupling agent) and several block copolymer branches emanating from it. The number of taps determined in laser angle scattering studies can vary widely, but is typically in the range of about 13 to about 22. In general, star polymers can be hydrogenated using any of the techniques known in the art for their utility in hydrogenating olefinic unsaturation. However, the hydrogenation conditions must be sufficient to hydrogenate at least 95% of the original olefinic unsaturation and the conditions must be applied such that the partially hydrogenated or fully hydrogenated polybutadiene blocks do not crystallize and separate from the solvent prior to hydrogenation or catalyst cleanup is completed. Depending on the percentage of butadiene used to form the star polymer, a significant increase in solution viscosity is sometimes noted during and after hydrogenation in cyclohexane. To avoid crystallization of the polybutadiene blocks, the temperature of the solvent must be maintained above the temperature at which crystallization could take place. In general, hydrogenation involves the use of a suitable catalyst as described in US-E-27145. Preferably, a mixture of nickel ethylhexanoate and triethylaluminum has 1.8 to 3 moles of aluminum per mole of nickel. To improve the viscosity index characteristics, the hydrogenated star polymers of this invention can be added to various lubricating oils. For example, selectively hydrogenated star polymers can be added to distillate petroleum fuels such as gas oils, synthetic and natural lubricating oils, crude oils and industrial oils. In addition to rotor oils, they can be used in the formulation of automatic transmission fluids, gear lubricants and hydraulic fluids. In general, any amount of selectively hydrogenated star polymers may be blended with the oils, with amounts in the range of about 0.05 to about 10 wt % being most common. For engine oils, amounts in the range of about 0.2 to about 2 wt. % are preferred. Lubricating oil compositions made using the hydrogenated star polymers of this invention may also contain other additives such as anti-corrosion additives, antioxidants, detergents, pour point depressants, and one or more additional VI modifiers. Conventional additives that would be useful in the lubricating oil composition of this invention and their description can be found in US-A-3772196 and US-A-3835083. Preferred embodiment of the invention
In the preferred star polymers of the present invention, the number average molecular weight (MW 1 ) of the outer polyisoprene block before hydrogenation is in the range of 15,000 to 65,000, the number average molecular weight (MW 2 ) of the polybutadiene block before hydrogenation is in the range of 2,000 to 6,000, the number average molecular weight (MW 3) the inner polyisoprene block is in the range of 5000 to 40000, the number average molecular weight (MWs) of the polystyrene block is in the range of 2000 to 4000 if the S block is external, and in the range of 4000 to 12000 if the S block is internal, and the star-shaped polymer contains less than 10 wt. % polybutadiene, and the ratio of MW 1 /MW 3 is in the range from 0.9:1 to 5:1. Polymerization of the polybutadiene block is preferably at least 89% with 1,4 addition. The star polymers of the present invention preferably have the (S-EP-EB-EP") n-X structure. The bound polymers are selectively hydrogenated with a nickel triethylaluminum ethylhexanoate solution having an Al/Ni ratio in the range of about 1.8:1 to 2.5: 1 to saturation of at least 98% of isoprene and butadiene units Having thus described the present invention as a whole and the preferred embodiment, the present invention is further described in the following examples, which are not intended to limit the invention.
Polymers 1 to 3 were obtained in accordance with the present invention. Resins 1 and 2 had internal polystyrene blocks and polymer 3 had an external polystyrene block on each arm of the star polymer. These polymers are compared with two polymers prepared in accordance with US-A-5460739, polymers 4 and 5, two commercial polymers, polymers 6 and 7, and a polymer prepared in accordance with US-A-5458791, polymer 8. Polymer compositions and The melt viscosities for these polymers are shown in Table 1. Polymers 1 and 2 clearly have melt viscosities that are superior to commercial polymers and those of US-A-5460739 and US-A-5458791. Polymer 3 has a melt viscosity superior to that of the polymers of US-A-5460739. The melt viscosity of polymer 3 is slightly lower than commercial star polymer 7, although the polymers have approximately the same polystyrene content. However, the total molecular weight of the branch, which is the sum of the molecular weights obtained in steps 1 to 4, for polymer 3 is lower than the total molecular weight of the branch of polymer 7, which is the sum of the molecular weights obtained in steps 1 and 2. If polymer 3 is modified by increasing the molecular weight obtained in steps 2, 3 or 4 so that the total molecular weight of the branch would approach the corresponding value for polymer 7, then it appears that the values of the melt viscosities would match or exceed the value of the melt viscosity of polymer 7 In general, polymers with high melt viscosities are easier to process with a cyclone. Polymer concentrates were made using Exxon HVI 100N LP base stock. The concentrates were used to prepare fully formulated SAE 10W-40 multipurpose oils. In addition to the VI modifier concentrate, these oils contained a pour point depressant, a dispersant inhibitor kit, and Shell HVI100N and HVI250N base oils. Diesel injector (DIN) lubricant viscosity loss test according to CECL-14-A-93 test procedure showed that polymers 1 to 3 are representative VI modifiers having high to intermediate mechanical shear resistance. These results are shown in Table 2. High shear viscosity, measured in a tapered bearing simulator (TBS) at 150° C., was typical of conventional star polymers having this level of permanent stability. This is important because results easily exceed the minimum required by SAE Standard J300. Polymers 1 and 3 matched the outstanding TPI-MRV performance of polymers 4 and 5. The SAE 10W-40 multipurpose oil that contained polymer 1 also exhibited a viscosity index time dependence. When stored at room temperature for three weeks, the viscosity index increased from 163 to 200. The kinematic viscosity at 100° C. did not change, but the viscosity at 40° C. decreased from 88 to 72 centistokes (from 88 to 72 mm 2 /s). Polymers 2 and 3 showed no time dependence. The polymer concentrates in Exxon HVI100N were also used to make fully formulated SAE 5W-30 multipurpose oils. These results are shown in Table 3. In addition to VI modifiers, these oils contained a pour point depressant, a dispersant inhibitor kit, and an additional Exxon HVI100N LP base oil. In the reproducibility of the TPI-MRV test at -35 o C, there was no significant difference in performance between polymers 1, 2 and 3 on the one hand, and 4 and 5 on the other, but they were all significantly better than polymer 8, as well as commercial polymers 6 and 7.
Claim
1. A star-shaped polymer having a structure selected from the group consisting of
(S-EP-EB-EP) n-X, (I)
(EP-S-EB-EP) n-X, (II)
(EP-EB-S-EP) n-X, (III)
where EP is an external hydrogenated block of polyisoprene having a number average mol.m before hydrogenation. (MW 1) between 6500 and 85000;
EB is a hydrogenated polybutadiene block having a number average mol.m. (MW 2) in the range between 1500 and 15000 and polymerized at least 85% by 1,4 addition;
EP" is an internal hydrogenated polyisoprene block having a number average molecular weight (MW 3) between 1500 and 55000 before hydrogenation;
S is a block of polystyrene having a number average mol.m. (MW s) in the range between 1000 and 4000 if the S block is external (I), and between 2000 and 15000 if the S block is internal (II or III);
where the star polymer structure contains from 3 to 15 wt.% polybutadiene, the ratio of MW 1 /MW 3 is in the range from 0.75:1 to 7.5:1, X is the core of the polyalkenyl coupling agent, and n is the number of branches block copolymers in a star polymer when linked to 2 or more moles of a polyalkenyl coupling agent per mole of living block copolymer molecules. 2. The star polymer of claim 1 wherein the polyalkenyl coupling agent is divinylbenzene. 3. The star polymer of claim 2, wherein n is the number of branches upon bonding to at least 3 moles of divinylbenzene per mole of living block copolymer molecules. 4. Star polymer according to claim 1, 2 or 3, where the number average mol.m. (MW 1) external polyisoprene block before hydrogenation is in the range from 15000 to 65000, number average mol.m. (MW 2) polybutadiene block before hydrogenation is in the range from 2000 to 6000, number average mol.m. (MW 3) internal polyisoprene block before hydrogenation is in the range from 5000 to 40000, number average mol.m. (W S) of the polystyrene block is in the range of 2000 to 4000 if the S block is external (I), and in the range of 4000 to 12000 if the S block is internal, the star polymer contains less than 10 wt.% polybutadiene, and the ratio MW 1 /MW 3 is in the range from 0.9:1 to 5:1. 5. A star polymer according to any one of the preceding claims, wherein the polymerization of the polybutadiene block is at least 89% by 1,4 addition. 6. The star polymer according to any one of the preceding claims, wherein the polyisoprene blocks and the polybutadiene blocks are at least 95% hydrogenated. 7. The composition of the oil, containing: base oil; and the amount of star polymer according to any one of the preceding paragraphs, modifying the viscosity index. 8. The concentrate of polymers for oil compositions, containing: at least 75 wt.% base oil; and from 5 to 25% by weight of a star polymer according to any one of claims 1 to 6.
Star-shaped polymer viscosity index modifier for oil compositions and oil compositions with it, shell engine oil, moth engine oil, engine oil 10w 40, engine oil difference, engine oil kinematic viscosity
