WO1998016566A1

WO1998016566A1 - New polymer in polymeric dispersion as a viscosity index improver

Info

Publication number: WO1998016566A1
Application number: PCT/EP1997/004993
Authority: WO
Inventors: Stephan Fengler; Horst Pennewiss; Stephan Massoth
Original assignee: Rohmax Additives Gmbh
Priority date: 1996-10-11
Filing date: 1997-09-12
Publication date: 1998-04-23
Also published as: ZA979103B; AU4384897A; EP0931101A1; JP2001503455A; DE19641954A1

Abstract

Disclosed is a solvent-free polymer-in-polymer dispersion consisting of polyalkyl(meth)acrylates (PAMA) and olefin copolymers (OCP), as well as their use as a viscosity index improver and a pour point depresser.

Description

N e u e Polymer i n Polymer-Di s p ersi o n a l s VI -ver s ererer

DESCRIPTION

State of the art

The invention describes a solvent-free polymer dispersion for use as a lubricating oil additive and for improving the viscosity index in lubricating oils. The technology uses large-scale lubricating oil additives based on oil-soluble polymers that improve the viscosity-temperature behavior of multigrade oils (VI improvers).

In addition to the thickening effect, adequate shear stability is expected from the polymers in question. In addition, the polymers should lower the pour point of the mineral oil as far as possible and have a dispersing and detergent effect on the sludge and dirt that accumulates in the engine. Two classes of polymers are used primarily for the above-mentioned tasks: lubricating oil additives based on polyalkyl methacrylates (PAMA) and olefin polypropylene (OCP), especially ethylene-propylene copolymers.

Both product classes have advantages and disadvantages. Olefin copolymers have an excellent thickening effect, but they have no pour point depressant action, so pour point improvers must be added to them. However, with certain, especially the association-prone association polyolefins, difficulties arise when adding pour point improvers. The difficulty lies in insufficiently lowering the pour point. Polymethacrylates are characterized by a good effect with regard to the viscosity temperature behavior of the oils thus improved and, when added in a sufficiently high concentration, also by an excellent wear protection effect. Also to be emphasized is their pour point depressing effect.

It was now considered to combine products from both polymer classes in order to create lubricating oil additives with improved properties. The technology expects to provide lubricating oil additives in liquid form (oil-based) with the highest possible absolute polymer content.

DE 29 05 954 describes that when a polymethacrylate solution in mineral oil is mixed with polyolefins, intolerance reactions can be observed beyond a certain limit: the polymers separate phases, which can lead to layer formation if stored for a sufficiently long time. To avoid such separation phenomena that make the product appear unusable, it has already been proposed to bring about compatibility between polyolefins and polymethacrylates by polymerizing the methacrylic acid esters in the solution of the polyolefin in oil.

It is also known that the alkyl methacrylate partially grafted onto the polyolefin. (DE 12 35491) DE 2363 792 recommends a solution to the compatibility problem shown above by combining compatible polymers.

According to Japanese patent application 50-111138, solution polymerizations of, for example, butyl acrylate and methyl methacrylate in the presence of a hydrogenated polybutadiene or a cyclopentadienethylene propylene rubber give stable polymer combinations. DE-OS 3822 134 describes a polymer composition which is suitable as a lubricating oil additive for improving the viscosity index and has the following composition:

a) an olefin copolymer with a molecular weight of approximately 30,000 to 200,000 daltons, b) a copolymer of olefins and acrylates and methacrylates c) a polyacrylate or polymethacrylate with a molecular weight of 20,000 to 500,000 daltons and d) a surfactant

The surface-active agent d) is an alkylene oxide adduct, which may contain nitrogen. The total polymer content of the preparation is 30-60% by weight, the rest of the preparation consists of mineral oil, for example neutral oil. The surfactant is also added dissolved in mineral oil.

However, the task of combining olefin copolymers with polymethylacrylates which combine the desired properties of both polymer classes and provide them in a form which meets the requirements of the trade and the additive technology has not been satisfactorily achieved by the prior art.

For reasons of economy, the highest possible polymer content of the commercial form is sought. In the desired high concentrations, PAMA solutions are relatively highly viscous, as are OCP solutions. There therefore appears to be no prospect of formulating the two product classes in a technically manageable mixture. It has now surprisingly been possible to produce a solvent-free polymer dispersion using the process according to the invention. Such a 100% polymer dispersion can be produced in a simple manner in a kneader, an extruder or in a static mixer. An outstanding property of these polymer dispersions is that they can be used both as a solid and in liquid form, dispersed with phase reversal in a suitable carrier medium, as a viscosity index improver.

The olefin copolymers according to the invention are known. These are primarily those which are composed of ethylene, propylene, butylene and / or isobutylene.

Such olefin copolymers are described, for example, in German Offenlegungsschriften DE 16 44 941, DE 17 69 834, DE 19 39 037, DE 19 63 039 and DE 20 59 981. Ethylene-propylene copolymers are preferred, and terpolymers with the addition of the known ter components such as ethylidene norbornene are also possible, but their tendency to crosslink during the aging process must also be taken into account.

The distribution of the monomer components in the copolymer can be largely statistical, but sequence polymers with ethylene blocks can also be used with advantages.

The ratio of the monomers ethylene to propylene is variable within certain limits, which can be set as the upper limit at approximately 70-75% by weight for ethylene and approximately 30-25% by weight for propylene. As a result of their reduced tendency to solubility in oil, polypropylene is already less suitable than ethylene-propylene copolymers.

The polyalkyl methacrylates are also known polymers which are composed of methacrylic esters with 6-22 carbon atoms in the alcohol radical, preferably those with 8-18 carbon atoms in the alcohol radical, optionally in minor additional amounts from further monomers which can be copolymerized with the methacrylic acid esters mentioned are. In the monomers to be added in minor amounts, usually below 20% by weight, it can on the one hand, for. B. are monomers with polar groups, in particular suitable polymerizable heterocyclic compounds which are known to contribute to the dispersion, detergent and detergent effects of the base polymers and the anti-wear effect of the base polymers. On the other hand, it can also be polyalkyl methacrylates with 1-5 carbon atoms in the alcohol residue. Methyl methacrylate and butyl methacrylate are particularly preferred.

Such monomers or copolymers with methacrylates are such. B. Part of the teaching of DE-PS 9 47 186, DE-PS 10 03 896, DE-AS 10 58 739 and DE-PS 17 45 359. Graft copolymers of polyolefins with polymerizable nitrogen-containing, in particular heterocyclic, compounds with dispersing action in addition Vl-improving effect are proposed in DE-AS 12 35 491. DE-OS 1 929 811 describes the graft copolymerization of degraded ethylene-propylene copolymers with oxygen-containing comonomers, such as vinyl esters of saturated carboxylic acids, for example vinyl acetate or divinyl esters of carboxylic acids. The exact structure of the graft copolymers obtained is not known; they can be used as additives in a wide variety of lubricants.

Vinylpyπdin, vinylpyrrolidine, vinylpyrrolidone and vinylimidazole - and derivatives thereof, in particular the alkylated heterocycles of this type - are particularly worth mentioning as heterocyclic monomers for copolymerization with the methacrylic acid esters mentioned. Among the nitrogen-containing monomers, 2- (4-morpholinyl) ethyl methacrylate is particularly preferred. These heterocyclic monomers can advantageously also be used in combination. PRODUCTION METHOD:

The polymer dispersions can be produced in a kneader, an extruder or in a static mixer. The treatment in the device reduces the molecular weight of the OCP under the influence of the shear forces, the temperature and the initiator concentration.

Examples of suitable initiators in the graft copolymerization are cumene hydroperoxide, diumyl peroxide, benzoyl peroxide, azodiisobutyric acid dinitrile, 2,2-bis (t-butyl peroxy) butane, diethyl peroxydicarbonate and tert-butyl peroxide. The processing temperature is between 80 ° C and 350 ° C. The residence time in the kneader or extruder is between 1 minute and 10 hours.

The longer the dispersion is treated in the kneader or extruder, the lower the molecular weight. The temperature and the concentration of free-radical initiators can be adjusted according to the desired molecular weight. The solvent-free polymer-in-polymer dispersion according to the invention can be converted into an easy-to-handle, liquid polymer / polymer emulsion by incorporation into suitable carrier media.

Suitable carrier media are described in DE 3207291. At this point, alkoxylated C8-C16 fatty alcohols and alkoxylated alkylphenols should be mentioned.

The liquid carrier medium used is one which allows the olefin copolymers to swell to a degree of 5-300% by weight in the temperature range between 40 and 150 ° C. ("degree of swelling"). The "degree of swelling" is defined as follows: An OCP film of 1 mm thickness, 2 cm length and 0.5 cm width of known weight is immersed at a different temperature - for example at 90 ° C. - and stored isothermally for 24 hours , removed from the solution with the tweezers, freed of the adhering swelling agent with a filter paper and immediately then balanced. The weight gain in percent - based on the initial weight - is defined as the measure of swelling. The swelling measurement should be carried out at the temperature at which the concentrated OCP emulsion is to be produced. At this temperature, the swelling should be 5-300%. A prerequisite for the applicability of the criterion is that the maximum swelling of the OCP has been reached under the conditions specified above. The degree of swelling is> 200% for good solvents and <100% for poor solvents.

The solvents that can be used as a liquid carrier medium should be inert and generally harmless. Carrier media that meet the conditions mentioned include, for. B. to the group of esters and / or to the group of higher alcohols. As a rule, the molecules of the types of compounds that can be used as carrier medium contain more than 8 carbon atoms per molecule.

The following should be emphasized in the group of esters: phosphoric acid esters, esters of dicarboxylic acids, esters of monocarboxylic acids with diols or polyalkylene glycols, esters of neopentyl polyols with monocarboxylic acids. (See Ulimann's Encyclopedia of Technical Chemistry, 3rd Edition, Vol. 15, pp. 287-292, Urban & Schwarzenber (1964)). Suitable esters of dicarboxylic acids are the esters of phthalic acid, in particular the phthalic esters with C4 to Cβ alcohols, dibutyl phthalate and dioctyl phthalate being particularly mentioned, and then the esters of aliphatic dicarboxylic acids, in particular the esters of straight-chain dicarboxylic acids with branched-chain primary alcohols. Particular emphasis is given to the esters of sebacic, adipic and azainic acid, the 2-ethylhexyl, isooctyl-3,5,5-trimethyl esters and the esters with the Cs, C9 and Cirj oxo alcohols being mentioned in particular should.

The esters of straight-chain primary alcohols with branched dicarboxylic acids are of particular importance. Examples include the alkyl-substituted adipic acid, for example 2,2,4-trimethyladipic acid. As alcohol component come with advantage such. B. the above-mentioned oxo alcohols in question. As esters of monocarboxylic acids with diols or polyalkylene glycols, the di-esters with diethylene glycol, triethylene glycol, tetraethylene glycol to decamethylene glycol, and also with dipropylene glycol as alcohol components should be emphasized. The monocarboxylic acids which are specifically mentioned are propionic acid, (iso) butyric acid and pelargonic acid - for example dipropylene glycol dipelargonate, diethylene glycol dipropionate - and diisobutyyrate as well as the corresponding esters of triethylene glycol and the tetraethylene glycol di-2-ethylhexanoic acid ester.

It should be mentioned that mixtures of the solvents described above are also suitable for the carrier medium. The proportion of the carrier medium in the concentrated polymer emulsion is generally 79 to 25% by weight, preferably less than 70, especially 60 to 40% by weight.

EXAMPLES

Example 1: Preparation of the polymer / polymer dispersion:

The following mixture is added to a thermostatted stamp kneader:

60 g ethylene-propylene copolymer

(70% by weight of ethylene, M _w = 200,000 g / mol) 40 g of methacrylic acid ester of a C10-C18 alcohol mixture

This mixture is homogenized at a temperature of 100 ° C. Then 2 g of 2,2-bis (t-butylperoxy) butane and 1 g of t-butylper-2-ethylhexanoate are added and the temperature is raised to 145 ° C. with kneading. After a reaction time of 20 minutes, the reaction mass is removed from the kneader. The product is tack-free up to approx. 50 ° C and can be easily traded in granular form.

The viscosity of a 1.7% by weight solution in mineral oil NS 100 corresponds to

100 ° C 11.4 mrτv7s 40 ° C 78.1 mm ² / s

Example 2: Transfer to a liquid polymer / polymer emulsion

50 g of the product prepared according to Example 1, 50 g of an ethylene-propylene copolymer (70% by weight of ethylene, M _w = 100,000 g / mol), 70 g of a C12-C14-fatty alcohol-polyethylene glycol ether mixture with an average degree of ethoxylation of 3 moles of ethylene oxide and 30 g of di-2-ethyl Hexyl adipate are placed in a round bottom flask with saber stirrer and emulsified at 130 ° C. The emulsification time is approx. 5 hours. After cooling to room temperature, a brownish white, low-viscosity emulsion is obtained. The polymer content of the emulsion is 50% by weight.

The viscosity at 5 s shear rate corresponds to

10 ° C 3900 mm ² / s

20 ° C 2500 mrrfVs

40 ° C 956 mm ² / s

100 ° C 1600 mm ² / s.

The viscosity of a 2.5% by weight solution in mineral oil NS 100 corresponds to

100 ° C 11.6 mm ² / s 40 ° C 78.3 mm ² / s

Example 3: Preparation of the emulsion in one step

60 g ethylene-propylene copolymer

(70% ethylene, M _w = 150,000 g / mol) 40 g methacrylic acid ester of a C10-C18 alcohol mixture

This mixture is homogenized at a temperature of 100 ° C. After a homogeneous mixture has been reached, 2 g of 2,2-bis (t-butylperoxy) butane and 1 g of t-butylper-2-ethylhexanoate are added and the temperature is increased to 145 ° C. with kneading. After a reaction time of 20 minutes, the mixture is mixed with 100 g of ethylene-propylene copolymer (70% ethylene, M _w = 200,000 g / mol) and 2 g of 2,2-bis (t-butylperoxy) butane were added and the mixture was kneaded at 145 ° C. for a further 20 minutes. The mixture is cooled to 130 ° C. Then 30 g of di-2-ethylhexyl adipate are added and kneaded until homogeneous. Then 70 g of a C12-C14-fatty alcohol-polyethylene glycol ether mixture with an average degree of ethoxylation of 3 mol ethylene oxide are added. This mixture is kneaded at 140 ° C for 2 hours. The mixture is then cooled to room temperature and removed from the kneader. A brownish-white, low-viscosity dispersion is obtained. The polymer content of the emulsion is 50% by weight.

The viscosity at 5 s shear rate corresponds to

10 ° C 3900 mm ² / s

20 ° C 2500 mm ² / s

40 ° C 956 mm ² / s

100 ° C 1600 mm ² / s

The viscosity of a 2.5% by weight solution in mineral oil NS 100 corresponds to

100 ° C 11.6 mm ² / s 40 ° C 78.3 mm / s

* SSI = shear stability index = loss of thickening effect in% with shear stability test according to DIN 51 382.

Claims

PATENT CLAIMS

1. Polymer / polymer (P- / P -) dispersion, characterized in that 2-60% by weight polyalkyl (meth) acrylate (PAMA) with a molecular weight of 5000-500,000 g / mol in a continuous olefin copolymer (OCP) - A phase with a molecular weight of 5,000 to 200,000 is dispersed, 5 to 100% by weight of the PAMA and the OCP being present in the form of a graft copolymer with a PAMA and OCP part as a phase stabilizer.

2. A process for the preparation of the phase stabilizer according to claim 1, characterized in that it consists of a graft copolymer of a polyalkyl (meth) acrylate and an olefin copolymer with a molecular weight of 5000-500,000 and that it is produced by reaction in the melt.

3. A process for the preparation of the P / P dispersion according to claim 1, characterized in that alkyl (meth) acrylates are polymerized in the presence of OCP without the addition of a solvent by adding a free radical initiator.

4. The method according to claim 3, characterized in that after the polymerization further OCP and initiator is added to the reaction mass.

5. The method according to claim 1-4, characterized in that 0 - 60 wt .-% of the alkyl (meth) acrylate used can be replaced by other monomers with a functional radical.

6. The method according to claim 5, characterized in that the other monomer with a functional radical is 2- (4-morpholinyl) - ethyl methacrylate.

7. The method according to claim 1-6, characterized in that the required molecular weight of the polymer is adjusted during the process.

8. A process for the preparation of a liquid polymer emulsion which is easy to handle at 10-40 ° C, characterized in that the P- / P dispersion according to claim 1 is emulsified in a carrier medium which is liquid at room temperature.

9. The method according to claim 1-8, characterized in that it is carried out in an extruder and / or kneader.

10. The method according to claim 8, characterized in that the liquid carrier medium consists of bad and good solvents for OCP.

11. The method according to claim 10, characterized in that the bad solvent for OCP is a good solvent for PAMA.

12. The method according to claim 10 and 11, characterized in that the poor solvent for OCP is a fatty alcohol polyalkylene glycol ether, alkylphenol polyethylene glycol ether or an oligomer based on alkyl (meth) acrylate.

13. Preparation according to one of claims 1-12, characterized in that it is cloudy.

14. Use of the products according to claims 1-12 as VI improvers for lubricants.