Process for producing alkyl (meth)acrylate homopolymers and copolymers having low residual monomer content

Abstract

The present invention relates to a process for producing alkyl (meth)acrylate homopolymers and copolymers having low residual monomer content, the alkyl (meth)acrylate homopolymers and copolymers obtained by this process, and their use in lubricant applications.

Description

[Technical Field]

[0001] The present invention relates to a process for producing alkyl (meth)acrylate homopolymers and copolymers having low residual monomer content, the alkyl (meth)acrylate homopolymers and copolymers obtained by this process, and their use in lubricant applications.

[0002] Reducing the residual monomer content is generally desired by polymer manufacturers, as products containing no or very low levels of residual monomer have a different commercial appeal. The presence of residual monomers can pose a risk to workers and sometimes even customers as a result of long-term exposure during polymer processing. Several known techniques exist for reducing the residual monomer content, such as additional initiator shots or post-processing treatments. Nevertheless, selecting the best or most appropriate technique is not always straightforward, and it is still observed that there is a relative lack of scientific literature on this issue. The technique to be used depends on the polymer application, which determines the purity grade, and the polymer quality, and some techniques for reducing the monomers may alter the polymer properties.

[0003] Unconverted or residual monomer is problematic for manufacturers of polyalkyl (meth)acrylates for a number of reasons.

[0004] Polymer is usually the desired product of the polymerization process, and therefore conversion should be as high as possible to maximize product performance and minimize specific product costs. High residual monomer content usually results in low conversion.

[0005] Residual monomer content affects the registration of a polymer, for example, for environmental and sustainability standards. The residual content of certain monomers or reactants, such as methyl methacrylate monomer, must be below certain limits for EU Ecolabel registration and should generally be as low as possible.

[0006] Small organic compounds have adverse effects on odor, flash point, and volatility (VOC).

[0007] The object of the present invention was therefore to reduce the total residual content of the monomer, i.e., methyl methacrylate, in polyalkyl(meth)acrylates to less than 10,000 ppm by weight, in order to achieve a higher conversion of the desired product and to avoid the drawbacks mentioned above.

[0008] technical level U.S. Patent No. 4,867,894 discloses the preparation of polyalkyl(meth)acrylate polymers by charging a mixture of different monomers into a reaction vessel and heating them. An initiator is then added, followed by a mixture of additional monomers and more initiator. There is no mention of adding additional monomers at the end of the reaction to reduce the residual monomer content.

[0009] U.S. Patent Application Publication No. 2008 / 0132663 discloses a method for free-radical polymerization of one or more ethylenically unsaturated compounds, in which at least 80% by weight of the ethylenically unsaturated compounds are initially charged and at least one polymerization initiator is added in at least two steps, with more initiator added in the second step than in the first step. Similarly, there is no mention of adding additional monomer at the end of the reaction to reduce the residual monomer content.

[0010] Prior art processes are unable to reduce the residual monomer content to the required level without subsequent expensive and time consuming vacuum degassing or stripping steps.

[0011] It has now been surprisingly found that adding an additional monomer, such as an alkyl (meth)acrylate, simultaneously with or shortly before the final addition of the free radical initiator shot is a suitable method for reducing the residual monomer content of the polymer product. Even more surprisingly, it has been found that the greatest reduction in residual monomer content occurs relative to the residual monomer content of methyl methacrylate, thereby improving odor and significantly increasing the flash point of the desired polymer.

[0012] The present invention modifies the process in a manner suitable to achieve the required levels without vacuum degassing or stripping operations.

[0013] The present invention can be used to prepare polymers of the same or different alkyl (meth)acrylates, as well as copolymers of the same or different alkyl (meth)acrylates with other comonomers other than alkyl (meth)acrylates, such as, for example, styrene, which polymers have minimized residual monomer content.

[0014] The low residual monomer content in the polymer makes it a favourable choice for lubricant formulations, including those that comply with EU Ecolabel requirements, for example.

[0015] EU Ecolabel standards limit the proportion of certain substances in the final product, in this case the lubricant formulation. The maximum treat rate of additives is defined accordingly.

[0016] Description of the Invention A first subject of the present invention is a method for producing a polyalkyl(meth)acrylate, comprising the steps of: (i) preparing a reaction mixture, the reaction mixture comprising: (A) at least two different alkyl (meth)acrylates; (B) optionally, a chain transfer agent, and (C) optionally, a base oil and (ii) charging the reaction mixture produced in step (i) into a reaction vessel; (iii) heating the reaction mixture to the desired reaction temperature; (iv) 0.1% to 4% by weight, preferably 0.1% to 2% by weight, of a free radical initiator, based on the total amount of monomers used. 1 either continuously or stepwise; (v) 0.05% to 0.2% by weight of initiator, based on the total amount of monomers used, after at least 95% monomer conversion has been achieved. 2 and adding less than 1 wt. %, preferably 0.5 wt. % or less of additional monomer to the reaction mixture based on the total amount of monomers used; (vi) optionally, further processing the reaction mixture to obtain the target polyalkyl(meth)acrylate; Including, For the purposes of the method, conversion is determined by measuring the residual monomer content by HPLC method.

[0017] According to the present invention, the residual monomer content was determined using the following HPLC method under the following test conditions: Detection: UV, 200 nm Column: LiChrospher 60-5 Si (125 mm x 3 mm, 5 μm) Eluent: n-hexane LiChr.:THFLiChr.=99.6:0.4 Flow rate: 0.9mL / min Injection volume: 20 μL

[0018] Quantification is performed using an external linear multipoint calibration with calibration standards corresponding to the monomer whose residual content is to be determined. Samples are prepared by adding 100 mg of the corresponding monomer to a 25 mL flask, which is then filled with the eluent.

[0019] In a further subject matter of the present invention, the alkyl(meth)acrylate (A) is (a) 0.2% by weight to 50% by weight of a C1-6 alkyl (meth)acrylate, preferably methyl methacrylate; (b) 50% to 99.8% by weight of a C7-20 alkyl (meth)acrylate, preferably a C10-15 alkyl methacrylate, more preferably a C12-14 alkyl methacrylate, and (c) 0% to 10% by weight of one or more further comonomers Includes:

[0020] In a further subject matter of the present invention, the alkyl(meth)acrylate (A) is (a) 0.2% to 25% by weight of a C1-6 alkyl (meth)acrylate, preferably methyl methacrylate; (b) 75% to 99.8% by weight of a C7-20 alkyl (meth)acrylate, preferably a C10-15 alkyl methacrylate, more preferably a C12-14 alkyl methacrylate, and (c) 0% to 10% by weight of one or more further comonomers Includes:

[0021] The content of each of components (a), (b), and (c) is based on the total amount of alkyl (meth)acrylate. In particular, the proportions of components (a), (b), and (c) total 100% by weight.

[0022] In a further subject matter of the present invention, the alkyl(meth)acrylate (A) is (a) 0.2% to 25% by weight of a C1-6 alkyl (meth)acrylate, preferably methyl methacrylate, and (b) 75% by weight to 99.8% by weight of a C7-20 alkyl (meth)acrylate, preferably a C10-15 alkyl methacrylate, more preferably a C12-14 alkyl methacrylate Includes:

[0023] In a further subject matter of the present invention, the alkyl(meth)acrylate (A) is (a) 10% to 15% by weight of a C1-6 alkyl (meth)acrylate, preferably methyl methacrylate, and (b) 85% to 90% by weight of a C7-20 alkyl (meth)acrylate, preferably a C10-15 alkyl methacrylate, more preferably a C12-14 alkyl methacrylate Includes:

[0024] The content of each of the components (a) and (b) is based on the total amount of alkyl (meth)acrylate. In particular, the proportions of the components (a) and (b) total 100% by weight.

[0025] The term "(meth)acrylate" refers to both esters of acrylic acid and esters of methacrylic acid. Methacrylates and mixtures of methacrylates and acrylates are preferred over acrylates.

[0026] C1-6 alkyl (meth)acrylates for use according to the invention are esters of (meth)acrylic acid and linear or branched alcohols having from 1 to 6 carbon atoms. The term "C1-6 alkyl (meth)acrylate" encompasses individual (meth)acrylic acid esters with alcohols of a particular length, as well as similar mixtures of (meth)acrylic acid esters with alcohols of different lengths.

[0027] Suitable C1-6 alkyl (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, and hexyl (meth)acrylate. Particularly preferred C1-6 alkyl (meth)acrylates are methyl (meth)acrylate and n-butyl (meth)acrylate, with methyl methacrylate being particularly preferred.

[0028] The C7-20 alkyl (meth)acrylates for use according to the invention are esters of (meth)acrylic acid and linear or branched alcohols having from 7 to 20 carbon atoms. The term "C7-20 alkyl methacrylate" encompasses individual (meth)acrylic acid esters with alcohols of a particular length, as well as similar mixtures of (meth)acrylic acid esters with alcohols of different lengths.

[0029] Suitable C7-20 alkyl (meth)acrylates include, for example, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, 2-propylheptyl (meth)acrylate, 2-butyloctyl (meth)acrylate, 2-hexyloctyl (meth)acrylate, decyl (meth)acrylate, 2-butyldecyl (meth)acrylate, 2-hexyldecyl (meth)acrylate, 2-octyldecyl (meth)acrylate, undecyl (meth)acrylate, 2-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, 2-methyldo ... decyl (meth)acrylate, 2-hexyldodecyl (meth)acrylate, 2-octyldodecyl (meth)acrylate, tridecyl (meth)acrylate, 2-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, 2-methylhexadecyl (meth)acrylate, heptadecyl (meth)acrylate, 5-isopropylheptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0030] C10-15 alkyl methacrylates for use in accordance with the present invention are esters of methacrylic acid with linear or branched alcohols having 10 to 15 carbon atoms. The term "C10-15 alkyl methacrylate" encompasses individual methacrylic acid esters with alcohols of a particular length, as well as similar mixtures of methacrylic acid esters with alcohols of different lengths.

[0031] Suitable C10-15 alkyl methacrylates include, for example, decyl methacrylate, 2-propylheptyl methacrylate, undecyl methacrylate, 2-methylundecyl methacrylate, dodecyl methacrylate, 2-methyldodecyl methacrylate, tridecyl methacrylate, 2-methyltridecyl methacrylate, tetradecyl methacrylate, and / or pentadecyl methacrylate.

[0032] Particularly preferred C10-15 alkyl methacrylates are methacrylic acid esters of linear C12-14 alkyl alcohol mixtures (C12-14 alkyl methacrylates), in particular lauryl methacrylate, branched C10-15 alkyl methacrylates, or mixtures of linear and branched C10-15 alkyl methacrylates.

[0033] Comonomers for use according to the present invention may be selected from the group consisting of styrene monomers having 8 to 17 carbon atoms, vinyl esters having 1 to 11 carbon atoms in the acyl group, vinyl ethers having 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates having 1 to 10 carbon atoms in the alcohol group, (di)alkyl maleates having 1 to 10 carbon atoms in the alcohol group, dispersing oxygen and nitrogen functionalized monomers, and mixtures of these monomers.

[0034] Examples of styrene monomers having 8 to 17 carbon atoms are styrene, substituted styrenes having alkyl substituents on the side chain, such as alpha-methylstyrene and alpha-ethylstyrene, substituted styrenes having alkyl substituents on the ring, such as vinyltoluene and para-methylstyrene, halogenated styrenes, such as monochlorostyrene, dichlorostyrene, tribromostyrene, and tetrabromostyrene, with styrene being preferred.

[0035] Examples of vinyl esters having 1 to 11 carbon atoms in the acyl group include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, and vinyl versatate. Preferred vinyl esters have 2 to 9, more preferably 2 to 5, carbon atoms in the acyl group. The acyl group may be linear or branched.

[0036] Examples of vinyl ethers having 1 to 10 carbon atoms in the alcohol group include, for example, vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl butyl ether, and vinyl octyl ether. Preferred vinyl ethers have 4 to 8 carbon atoms in the alcohol group. Here, the alcohol group may be linear or branched.

[0037] The term "(di)ester" means that monoesters, diesters, and mixtures of esters, especially fumaric and / or maleic acid, can be used. (Di)alkyl fumarates having 1 to 10 carbon atoms in the alcohol group include monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, methylethyl fumarate, monobutyl fumarate, dibutyl fumarate, dipentyl fumarate, and dihexyl fumarate. Preferred (di)alkyl fumarates contain 1 to 8, more preferably 1 to 4, carbon atoms in the alcohol group. Here, the alcohol group may be linear or branched.

[0038] (Di)alkyl maleates having 1 to 10 carbon atoms in the alcohol group include monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, methylethyl maleate, monobutyl maleate, and dibutyl maleate. Preferred (di)alkyl maleates have 1 to 8, more preferably 1 to 4, carbon atoms in the alcohol group. Here, the alcohol group may be linear or branched.

[0039] Examples of dispersible oxygen-functionalized monomers are hydroxyalkyl (meth)acrylates, such as 3-hydroxypropyl (meth)acrylate, 3,4-dihydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,5-dimethyl-1,6-hexanediol (meth)acrylate, and 1,10-decanediol (meth)acrylate.

[0040] Examples of dispersible nitrogen-functionalized monomers are aminoalkyl(meth)acrylates, such as N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, N,N-diethylaminopentyl(meth)acrylate, N,N-dibutylaminohexadecyl(meth)acrylate; aminoalkyl(meth)acrylamides, such as N,N-dimethylaminopropyl(meth)acrylamide; heterocyclic(meth)acrylates, such as 2-(1-imidazolyl)ethyl(meth)acrylate, 2-(4-morpholinyl)ethyl(meth)acrylate, 1-(2-methacryloyloxyethyl)-2-pyrrolidone, N-methacryloylmorpholine, N-methacryloyl-2-pyrrolidinone, N-( 2-methacryloyloxyethyl)-2-pyrrolidinone, N-(3-methacryloyloxypropyl)-2-pyrrolidinone; heterocyclic vinyl compounds such as 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinyloxazole, and hydrogenated vinyloxazole.

[0041] The N-dispersant monomer may specifically be at least one monomer selected from the group consisting of N-vinylpyrrolidinone, N,N-dimethylaminoethyl methacrylate, and N,N-dimethylaminopropyl methacrylamide.

[0042] The polyalkyl (meth)acrylate polymers produced according to the present invention have a weight average molecular weight in the range of 10,000 g / mol to 600,000 g / mol, preferably 20,000 g / mol to 200,000 g / mol, and more preferably 30,000 g / mol to 150,000 g / mol. The polyalkyl (meth)acrylate polymers according to the present invention have a number average molecular weight in the range of 5,000 g / mol to 200,000 g / mol, preferably 10,000 g / mol to 80,000 g / mol, and more preferably 15,000 g / mol to 60,000 g / mol.

[0043] Preferably, the polyalkyl(meth)acrylate polymers according to the present invention have a polydispersity index (PDI) M in the range of 1.5 to 3.5, more preferably in the range of 1.8 to 2.5. w / M n It has.

[0044] M w and M n is determined by size exclusion chromatography (SEC) using commercially available polymethyl methacrylate standards. Measurements are performed by gel permeation chromatography using THF as the eluent.

[0045] Suitable chain transfer agents (B) are in particular oil-soluble mercaptans, such as n-dodecyl mercaptan, tert-dodecyl mercaptan, 2-mercaptoethanol, and 2-ethylhexyl-thioglycolate, preferably n-dodecyl mercaptan, tert-dodecyl mercaptan, or 2-mercaptoethanol, or else chain transfer agents from the class of terpenes, such as terpinolene, with n-dodecyl mercaptan being preferred.

[0046] The base oils (C) to be used in the present invention may be selected from the group consisting of API Group I, II, III, IV, V oils and mixtures thereof. They are preferably selected from API Group V oils or from API Group I, II or III oils and mixtures thereof. API Group II oils are most preferred.

[0047] The reaction vessel mentioned in step (ii) can be any suitable reaction vessel equipped with a stirrer and a temperature control system under an inert gas, preferably under a nitrogen atmosphere.

[0048] The reaction temperature mentioned in step (iii) is generally in the range of from 20° C. to 200° C., preferably from 90° C. to 120° C. The polymerization can be carried out at ambient, reduced or elevated pressure, with either ambient or elevated pressure being preferred.

[0049] One, two, three, or more types of free radical initiators can be used separately or in combination. Initiators Used According to the Invention 1 and an initiator 2may be the same or different and include azo initiators such as azobis-isobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile) (AMBN) and 1,1-azobiscyclohexanecarbonitrile, and peroxy compounds such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tert-butyl per-2-ethylhexanoate, ketone peroxide, tert-butyl peroctoate, methyl isobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxyisopropyl carbonate, 2,5-bis(2-ethylhexanoylperoxy) )-2,5-dimethylhexane, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxy-3,5,5-trimethylhexanoate, dicumyl peroxide, 1,1-bis(tert-butylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumyl hydroperoxide, tert-butyl hydroperoxide, bis(4-tert-butylcyclohexyl)peroxydicarbonate and 2,2-di(tert-butylperoxy)butane, as well as mixtures of two or more of the foregoing compounds with one another, and mixtures of the foregoing compounds with unspecified compounds that are also capable of forming free radicals.

[0050] Preferred Initiators 1 and 2are independently selected from the group consisting of 2,2'-azobis(2-methylbutyronitrile), tert-butylperoxy-2-ethylhexanoate, tert-amylperoxy-2-ethylhexanoate, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, tert-butylperoxybenzoate, 2,2-di(tert-butylperoxy)butane, and tert-butylperoxy-3,5,5-trimethylhexanoate, more preferably tert-butylperoxy-2-ethylhexanoate and tert-amylperoxy-2-ethylhexanoate. 1 and 2 As the peroxy group, tert-butylperoxy-2-ethylhexanoate is particularly preferred.

[0051] The additional alkyl (meth)acrylate mentioned in step (v) may be selected from the group consisting of C4-14 alkyl acrylate, C4-14 alkyl methacrylate, C4-14 alkyl maleate, C4-14 alkyl fumarate, and styrene. 2-Ethylhexyl acrylate, styrene, and C12-14 alkyl acrylate (lauryl acrylate) are preferred, and C4-14 alkyl acrylate and styrene are preferred.

[0052] These are preferably oil-soluble and more reactive than most alkyl (meth)acrylates (A) used to prepare polymers capable of forming oil-soluble homopolymers. More preferred are alkyl (meth)acrylates that exhibit good reactivity with residual methyl methacrylate.

[0053] The additional monomer is preferably selected from the group consisting of 2-ethylhexyl acrylate, lauryl methacrylate, and styrene, more preferably 2-ethylhexyl acrylate and styrene.

[0054] The phrase "after at least 95% monomer conversion has been achieved" refers to the final stage of polymerization, indicated by a slowdown in the heat release due to the reaction. At this point, the residual monomer content in the product is less than 5% (corresponding to at least 95% monomer conversion), typically between 1% and 5% of the total amount of monomer used in the reaction.

[0055] Correspondingly, the conversion was determined by measuring the residual monomer content by the HPLC method, as described above.

[0056] The base oils used in accordance with the present invention include oils of lubricating viscosity, including natural and synthetic oils, oils derived from hydrocracking, hydrogenation and hydrofinishing, unrefined oils, refined oils, rerefined oils, or mixtures thereof.

[0057] Base oils may also be defined as specified by the American Petroleum Institute (API) (see Appendix E-API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils, April 2008 edition, section 1.3 Subheading 1.3. Base Stock Categories).

[0058] API currently defines five groups of lubricant base stocks (API 1509, Annex E - API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils, September 2011). Groups I, II, and III are mineral oils, which are classified by the amount of saturates and sulfur they contain and their viscosity index; Group IV is polyalphaolefins; and Group V is everything else, including ester oils, etc. The table below shows these API classifications.

[0059] [Table 1]

[0060] The kinematic viscosity (KV) at 100°C of suitable non-polar base oils used in accordance with the present invention 100 ) is determined in accordance with ASTM D445 and is preferably 1 mm 2 / s~20mm 2 / s, and more preferably 1 mm 2 / s~10mm 2 / s, and more preferably 1 mm 2 / s~5mm 2 / s range.

[0061] Further base oils that can be used in accordance with the present invention are Group II-III Fischer-Tropsch derived base oils.

[0062] Fischer-Tropsch derived base oils are known in the art. The term "Fischer-Tropsch derived" means that the base oil is or is derived from the synthesis product of the Fischer-Tropsch process. Fischer-Tropsch derived base oils may also be referred to as GTL (Gas-to-Liquid) base oils. Suitable Fischer-Tropsch derived base oils which may be advantageously used as the base oil for the compressor oil of the present invention are, for example, those disclosed in EP 0 776 959, EP 0 668 342, WO 97 / 21788, WO 00 / 15736, WO 00 / 14188, WO 00 / 14187, WO 00 / 14183, WO 00 / 14179, WO 00 / 08115, WO 99 / 41332, EP 1 029 029, WO 01 / 18156, WO 01 / 57166 and WO 2013 / 189951.

[0063] The polyalkyl(meth)acrylates produced by the process of the present invention can be further processed. The further reaction steps can be selected from the group consisting of diluting the polyalkyl(meth)acrylate to obtain a lower solids content in the base oil, concentrating to obtain a higher solids content in the base oil, filtering the reaction mixture, degassing the reaction mixture (stripping, removing volatile components), or blending the reaction mixture with additional components such as other polymers.

[0064] The polymers produced by the process of the present invention are characterized by low residual monomer content.

[0065] A further object of the present invention is a method for producing a polyalkyl(meth)acrylate, comprising the steps of: (i) preparing a reaction mixture, (A) at least two different alkyl (meth)acrylates, (a) 0.2% to 25% by weight of a C1-6 alkyl (meth)acrylate, preferably methyl methacrylate, and (b) 75% by weight to 99.8% by weight of a C7-20 alkyl (meth)acrylate, preferably a C10-15 alkyl methacrylate, more preferably a C12-14 alkyl methacrylate at least two different alkyl (meth)acrylates comprising (B) optionally, a chain transfer agent, and (C) optionally, a base oil and (ii) charging the reaction mixture produced in step (i) into a reaction vessel; (iii) heating the reaction mixture to the desired reaction temperature; (iv) 0.1% to 4% by weight, preferably 1% to 2% by weight, of a free radical initiator, based on the total amount of monomers used. 1 either continuously or stepwise; (v) 0.05% to 0.2% by weight of initiator, based on the total amount of monomers used, after at least 95% monomer conversion has been achieved. 2 and adding less than 1 wt. %, preferably 0.5 wt. % or less of additional monomer to the reaction mixture based on the total amount of monomers used; (vi) optionally, further processing the reaction mixture to obtain the target polyalkyl(meth)acrylate; Including, The conversion is determined by measuring the residual monomer content by HPLC method (as described above). The purpose is to

[0066] A further object of the present invention is a method for producing a polyalkyl(meth)acrylate, comprising the steps of: (i) preparing a reaction mixture, the reaction mixture comprising: (A) at least two different alkyl (meth)acrylates, (a) 10% to 15% by weight of a C1-6 alkyl (meth)acrylate, preferably methyl methacrylate, and (b) 85% to 90% by weight of a C7-20 alkyl (meth)acrylate, preferably a C10-15 alkyl methacrylate, more preferably a C12-14 alkyl methacrylate at least two different alkyl (meth)acrylates comprising (B) optionally, a chain transfer agent, and (C) optionally, a base oil and (ii) charging the reaction mixture produced in step (i) into a reaction vessel; (iii) heating the reaction mixture to the desired reaction temperature; (iv) 0.1% to 4% by weight, preferably 0.1% to 2% by weight, of a free radical initiator, based on the total amount of monomers used. 1 either continuously or stepwise; (v) 0.05% to 0.2% by weight of initiator, based on the total amount of monomers used, after at least 95% monomer conversion has been achieved. 2 and adding less than 1 wt. %, preferably 0.5 wt. % or less of additional monomer to the reaction mixture based on the total amount of monomers used; (vi) optionally, further processing the reaction mixture to obtain the target polyalkyl(meth)acrylate; Including, The conversion is determined by measuring the residual monomer content by HPLC method (as described above). The purpose is to

[0067] A further object of the present invention is directed to polyalkyl(meth)acrylates produced by the process as described hereinbefore and having a total residual monomer content of less than 1% by weight, preferably less than 0.7% by weight, and in the case of copolymers containing methyl methacrylate, a residual methyl methacrylate content of less than 0.1% by weight, preferably less than 0.07% by weight, the residual monomer content being determined by the HPLC method as described above.

[0068] The reduction in residual monomer content was improved by more than 10% in all cases.

[0069] A further object of the present invention is directed to polyalkyl(meth)acrylates produced by the method as described hereinabove and having a flash point higher than the flash point of polyalkyl(meth)acrylates produced without step (v) in the production process.

[0070] The viscosity of the resulting polymer solution is adjusted to a range of 200 cSt to 2000 cSt by adjusting the proportion of base oil or diluent oil (C).

[0071] To ensure the most cost-effective use of viscosity modifiers, the polymer thickening efficiency (TE) is important. TE represents the increase in kinematic viscosity at 100°C of an oil after adding a specific amount of polymer.

[0072] Thickening efficiency is primarily a function of the chemical structure and molecular weight of the polymer: larger molecules are better thickeners than smaller molecules, and at the same molecular weight, some polymer chemical structures are better thickeners than others.

[0073] The polyalkyl(meth)acrylates produced according to the invention have a thickening efficiency at 100° C. that is comparable to or slightly improved over non-inventive products. This slight increase is related to the reduced residual monomer content of the inventive products.

[0074] A further object of the present invention is directed to the use of polyalkyl(meth)acrylates produced by the process as described hereinbefore as additives in industrial fluids.

[0075] A further object of the present invention is 1. An industrial fluid comprising: (A) 0.5% to 50% by weight of a polyalkyl(meth)acrylate produced by the method described previously herein; (B) 50% to 99.5% by weight of a base oil selected from the group consisting of API Group I, II, III, IV and V oils, and mixtures thereof, preferably API Group I, II, III oils, and mixtures thereof; (C) 0% to 5% by weight of one or more further additives; Intended for industrial fluids, including

[0076] A further object of the present invention is 1. An industrial fluid comprising: (A) 0.5% to 25% by weight of a polyalkyl(meth)acrylate prepared by the method described previously herein; (B) 75% to 99.5% by weight of a base oil selected from the group consisting of API Group I, II, III, IV, and V oils, and mixtures thereof; (C) 0% to 5% by weight of one or more further additives; Intended for industrial fluids, including

[0077] A further object of the present invention is an industrial fluid complying with the requirements of the EU Ecolabel, comprising: (A) 0.5% to 13% by weight of a polyalkyl(meth)acrylate prepared by the method described previously herein; (B) 87% to 99.5% by weight of a biodegradable base oil selected from the group consisting of API Group IV and V oils, which are vegetable oils, and mixtures thereof, preferably selected from API Group IV and V oils, and mixtures thereof; (C) 0% to 5% by weight of one or more further additives; Intended for industrial fluids, including

[0078] The amount of each component (A), (B), and (C) is based on the total composition of the lubricating oil composition, and in certain embodiments, the percentages of components (A), (B), and (C) total 100 wt.%.

[0079] The biodegradable base oil is selected from the group consisting of vegetable oils, polyalkylene glycols, and synthetic esters.

[0080] Suitable commonly used vegetable oils are soybean oil, rapeseed oil, cottonseed oil, olive oil, sunflower oil, and canola oil.

[0081] The polyalkylene glycol may be selected from API Group V base oils and mixtures thereof, and the synthetic ester may be selected from API Group V base oils and mixtures thereof.

[0082] The industrial fluids according to the present invention may also contain, as component (C), further additives selected from the group consisting of conventional VI improvers, dispersants, antifoam agents, detergents, antioxidants, pour point depressants, antiwear additives, extreme pressure additives, friction modifiers, anticorrosion additives, dyes, and mixtures thereof.

[0083] Conventional VI improvers include hydrogenated styrene-diene copolymers (HSD, U.S. Pat. Nos. 4,116,917, 3,772,196, and 4,788,316), especially based on butadiene and isoprene, and also olefin copolymers (OCPs, K. Marsden: Literature Review of OCP Viscosity Modifiers, Lubrication Science 1 (1988), 265), in particular those of the poly(ethylene-co-propylene) type, which may also frequently be present in N / O-functional form, having dispersant action, or PAMA, which is usually present in N-functional form, having advantageous additive properties (boosters) as dispersants, wear protection additives, and / or friction modifiers (Roehm and Haas, DE 1 520 696; RohMax Additives, WO 2006 / 007934).

[0084] Compilations of VI improvers and pour point depressants for lubricating oils, in particular motor oils, are detailed, for example, in T. Mang, W. Dresel (eds.): "Lubricants and Lubrication", Wiley-VCH, Weinheim 2001; R.M. Mortier, S.T. Orszulik (eds.): "Chemistry and Technology of Lubricants", Blackie Academic & Professional, London 1992; or J. Bartz: "Additive für Schmierstoffe", Expert-Verlag, Renningen-Malmsheim 1994.

[0085] Suitable dispersants include poly(isobutylene) derivatives, such as poly(isobutylene) succinimide (PIBSI), including borated PIBSI, and ethylene-propylene oligomers with N / O functionality.

[0086] Dispersants (including borated dispersants) are preferably used in an amount of 0 to 5 wt %, based on the total weight of the lubricating oil composition.

[0087] Suitable antifoaming agents include silicone oils, fluorosilicone oils, fluoroalkyl ethers, and the like.

[0088] The antifoaming agent is preferably used in an amount of 0.005 to 0.1% by weight, based on the total amount of the lubricating oil composition.

[0089] Preferred detergents include metal-containing compounds such as phenoxides; salicylates; thiophosphonates, especially thiopyrophosphonates, thiophosphonates, and phosphonates; sulfonates and carbonates. As metals, these compounds may contain, in particular, calcium, magnesium, and barium. These compounds may preferably be used in neutral or overbased form.

[0090] The detergent is preferably used in an amount of 0.2 to 1% by weight, based on the total amount of the lubricating oil composition.

[0091] Suitable antioxidants include, for example, phenolic antioxidants and amine antioxidants.

[0092] Examples of phenolic antioxidants include octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-bis(2,6-di-t-butylphenol); 4,4'-bis(2-methyl-6-t-butylphenol); 2,2'-methylenebis(4-ethyl-6-t-butylphenol); 2,2'-methylenebis(4-methyl-6 -t-butylphenol;4,4'-butylidenebis(3-methyl-6-t-butylphenol);4,4'-isopropylidenebis(2,6-di-t-butylphenol);2,2'-methylenebis(4-methyl-6-nonylphenol);2,2'-isobutylidenebis(4,6-dimethylphenol);2,2'-methylenebis(4-methyl-6-cyclohexylphenol);2,6-di-t-butyl-4-methylphenol;2,6 -Di-t-butyl-4-ethyl-phenol;2,4-dimethyl-6-t-butylphenol;2,6-di-t-amyl-p-cresol;2,6-di-t-butyl-4-(N,N'-dimethylaminomethylphenol);4,4'-thiobis(2-methyl-6-t-butylphenol);4,4'-thiobis(3-methyl-6-t-butylphenol);2,2'-thiobis(4-methyl-6-t-butylphenol);Bis(3-methyl-4- hydroxy-5-t-butylbenzyl) sulfide; bis(3,5-di-t-butyl-4-hydroxybenzyl) sulfide; n-octyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate; n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate; 2,2'-thio[diethyl-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], etc. Among these, bisphenol-based antioxidants and ester group-containing phenol-based antioxidants are particularly preferred.

[0093] Examples of the amine antioxidant include monoalkyldiphenylamines such as monooctyldiphenylamine and monononyldiphenylamine; dialkyldiphenylamines such as 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, and 4,4'-dinonyldiphenylamine; polyalkyldiphenylamines such as tetrabutyldiphenylamine and tetrahexyldiphenylamine; naphthylamines, specifically alpha-naphthylamine, phenyl-alpha-naphthylamine, and further alkyl-substituted phenyl-alpha-naphthylamines, such as butylphenyl-alpha-naphthylamine, pentylphenyl-alpha-naphthylamine, hexylphenyl-alpha-naphthylamine, heptylphenyl-alpha-naphthylamine, octylphenyl-alpha-naphthylamine, nonylphenyl-alpha-naphthylamine, etc. Among these, diphenylamine is preferred over naphthylamine in terms of its antioxidant effect.

[0094] Suitable antioxidants may further be selected from the group consisting of sulfur- and phosphorus-containing compounds, such as metal dithiophosphates, e.g., zinc dithiophosphate (ZnDTP), "OOS triesters" = reaction products of dithiophosphoric acids with activated double bonds from olefins, cyclopentadiene, norbornadiene, alpha-pinene, polybutenes, acrylic esters, maleic esters (ashless on combustion); organic sulfur compounds, e.g., dialkyl sulfides, diaryl sulfides, polysulfides, modified thiols, thiophene derivatives, xanthates, thioglycols, thioaldehydes, sulfur-containing carboxylic acids; heterocyclic sulfur / nitrogen compounds, in particular dialkyldimercaptothiadiazoles, 2-mercaptobenzimidazoles; zinc bis(dialkyldithiocarbamates), and methylene bis(dialkyldithiocarbamates); organic phosphorus compounds, e.g., triaryl and trialkyl phosphites; organic copper compounds, and overbased calcium and magnesium-based phenoxides and salicylates.

[0095] The antioxidant is used in an amount of 0 to 15% by weight, preferably 0.1 to 10% by weight, more preferably 0.2 to 2% by weight, based on the total amount of the lubricating oil composition.

[0096] Pour point depressants include ethylene-vinyl acetate copolymers, chlorinated paraffin-naphthalene condensates, chlorinated paraffin-phenol condensates, polymethacrylates, polyalkylstyrenes, etc. Polymethacrylates having a weight average molecular weight of 5,000 to 50,000 g / mol are preferred.

[0097] The amount of pour point depressant is preferably 0.1 to 1 wt %, based on the total amount of the lubricating oil composition.

[0098] Preferred antiwear and extreme pressure additives are sulfur-containing compounds, such as zinc dithiophosphate, zinc diC 3~12alkyldithiophosphates (ZnDTP), zinc phosphate, zinc dithiocarbamate, molybdenum dithiocarbamate, molybdenum dithiophosphate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, polysulfides, etc.; phosphorus-containing compounds, such as phosphites, phosphates, for example, trialkyl phosphates, triaryl phosphates, for example, tricresyl phosphate, amine-neutralized mono- and dialkyl phosphates, ethoxylated mono- and dialkyl phosphates, phosphonates, phosphines, amine salts or metal salts of these compounds, etc.; sulfur- and phosphorus-containing antiwear agents, such as thiophosphites, thiophosphates, thiophosphonates, amine salts or metal salts of these compounds, etc.

[0099] The antiwear agent may be present in an amount of 0 to 3 wt %, preferably 0.1 to 1.5 wt %, more preferably 0.2 to 0.9 wt %, based on the total amount of the lubricating oil composition.

[0100] The friction modifiers used may include mechanically active compounds such as molybdenum disulfide, graphite (including fluorinated graphite), poly(trifluoroethylene), polyamides, polyimides; compounds that form adsorbed layers such as long-chain carboxylic acids, fatty acid esters, ethers, alcohols, amines, amides, imides; compounds that form layers through tribochemical reactions such as saturated fatty acids, phosphate esters and thiophosphate esters, xanthogenates, sulfurized fatty acids; compounds that form polymeric layers such as ethoxylated dicarboxylic acid partial esters, dialkyl phthalates, methacrylates, unsaturated fatty acids, sulfurized olefins or organometallic compounds such as molybdenum compounds (molybdenum dithiophosphate and molybdenum dithiocarbamate MoDTC) and combinations thereof with ZnDTP, copper-containing organic compounds.

[0101] Friction modifiers may be used in an amount of 0 to 6 wt %, preferably 0.05 to 4 wt %, more preferably 0.1 to 2 wt %, based on the total amount of the lubricating oil composition.

[0102] Some of the compounds listed above may perform multiple functions: for example, ZnDTP is primarily an antiwear and extreme pressure additive, but also has the characteristics of an antioxidant and corrosion inhibitor (here, a metal passivator / deactivator).

[0103] The additives listed above are described in detail, inter alia, in T. Mang, W. Dresel (eds.): "Lubricants and Lubrication", Wiley-VCH, Weinheim 2001; RM Mortier, ST Orszulik (eds.): "Chemistry and Technology of Lubricants". [Brief explanation of the drawings]

[0104] [Figure 1] The residual monomer content in the products of Experiments 1 to 8 is shown. [Figure 2] The reduction in total residual monomer content in runs 1 to 8 is shown. [Figure 3] The reduction in residual methyl methacrylate content in Runs 1 to 8 is shown. [Figure 4] The correlation between the flash point of the polymer and the increasing concentration of residual MMA is shown.

[0105] The present invention is further illustrated by the following non-limiting examples.

[0106] Experimental section Abbreviation C10-15AMA C12-15 Alkyl Methacrylate, 77% Branched and 23% Linear (Average molecular weight=279g / mol) nDDM n-dodecyl mercaptan tDDM tert-dodecyl mercaptan EHA 2-Ethylhexyl Acrylate HPLC High Performance Liquid Chromatography KV Kinematic viscosity measured by ASTM D445 KV100 Kinematic viscosity measured at 100°C according to ASTM D445 LIMA C12-15 Alkyl Methacrylate, 60% Branched and 40% Linear (molecular weight=273g / mol) LMA Lauryl methacrylate, 73% C12, 27% C14; all linear (molecular weight=262g / mol) MMA Methyl methacrylate (molecular weight = 100.12 g / mol) M w Weight average molecular weight M n number average molecular weight PDI Polydispersity Index1 ReMo residual monomer(s) Sty Styrene TBPEH tert-butyl peroxy-2-ethylhexanoate TE: Thickening efficiency measured as kinematic viscosity at 100°C in test oil

[0107] Test Method The polyalkyl(meth)acrylates produced according to the present invention and comparative examples were characterized with respect to their molecular weight, PDI, and their bulk viscosity.

[0108] The molecular weight and polydispersity of polyalkyl(meth)acrylates can be determined by known methods. For example, gel permeation chromatography (GPC) can be used. It is also possible to use osmometry, such as gas phase osmometry, to determine the molecular weight. The methods described are described, for example, in PJ Flory, "Principles of Polymer Chemistry" Cornell University Press (1953), Chapter VII, 266-316, and in "Macromolecules, an Introduction to Polymer Science", FA Bovey and FH Winslow, Editors, Academic Press (1979), 296-312, and in WW Yau, JJ Kirkland and DD Bly, "Modern Size Exclusion Liquid Chromatography", John Wiley and Sons, New York, 1979. It is preferable to use gel permeation chromatography to determine the molecular weight of the polymers presented herein.

[0109] The weight average molecular weight (M w ) was determined by gel permeation chromatography (GPC) using polymethyl methacrylate calibration standards according to DIN 55672-1 using the following measurement conditions: Eluent: Tetrahydrofuran (THF), continuously distilled and circulated by pump Oven temperature: 35°C Columns: The column set consisted of four columns: two columns SDV 106Å, one column SDV 104Å, and one column SDV 103Å (PSS Standards Service GmbH, Mainz, Germany), all with dimensions of 300 × 8 mm and an average particle size of 10 μm. Flow rate: 1mL / min Injection volume: 100 μL Equipment: Agilent 1100 series consisting of autosampler, pump, and column oven Detection device: Agilent 1260 series refractive index detector.

[0110] According to the present invention, the residual monomer content was determined using the following HPLC method under the following test conditions: Detection: UV, 200 nm Column: LiChrospher 60-5 Si (125 mm x 3 mm, 5 μm) Eluent: n-hexane LiChr. :THF LiChr. =99.6:0.4 Flow rate: 0.9mL / min Injection volume: 20 μL

[0111] Quantification is performed using an external linear multipoint calibration with calibration standards corresponding to the monomer whose residual content is to be determined. Samples are prepared by adding 100 mg of the corresponding monomer to a 25 mL flask, which is then filled with the eluent.

[0112] General Polymerization Procedure 1 (Examples 1 to 9) A reaction mixture was prepared by combining 187.72 g (1.87 mol; 13.0% based on the total amount of monomers used) of methyl methacrylate, 1256.28 g (4.80 mol; 87.0% based on the total amount of monomers used) of lauryl methacrylate, 10.4 g (0.72% based on the total amount of monomers used) of the chain transfer agent nDDM, and 556 g of paraffin oil (Chevron 100N).

[0113] The mixture was charged into a 3-liter reactor equipped with a thermometer, temperature controller, addition funnel, purge gas inlet, and water-cooled reflux condenser with a purge gas outlet, then inerted with dry ice (CO) and heated to 110°C in a nitrogen flow of 15 L / h with an agitator speed of 150 rpm. Once the reaction temperature was reached, a total of 14.44 g (1% based on the total amount of monomers used) of initiator mixture (3.61 g; 0.25% based on the total amount of monomers used) in 10.83 g of paraffin oil (Chevron 100N) was added in three steps: 5% of the initiator solution in the first hour, 25% in the second hour, and 70% in the third hour. After all the initiator solution was charged, the mixture was cooled to 100°C over a 1-hour hold period.

[0114] The above process yielded 1994.23 g polymer solution having a crude polymer solids content of about 71.2 wt %.

[0115] Post-treatment of the polymer solution is described below.

[0116] Post-treatment of polymer solution 1 After holding at 100°C for 1 hour, the sample was treated with an initiator solution (1.44 g of tert-butyl peroxy-2-ethylhexanoate in 4.33 g of paraffin oil Chevron 100N) and 3.6 g or 7.2 g of additional monomer in portions, immediately followed by the addition of initiator. An additional 1-hour holding period followed.

[0117] The described process yielded 2000 g (without additional monomer) or 2003.6 g and 2007.2 g (with additional monomer added) of polymer solution, respectively, with crude polymer solids contents ranging from 72.2% to 72.6%, respectively.

[0118] General Polymerization Procedure 2 (Examples 10-14) A reaction mixture was prepared by combining 1980.8 g (7.26 mol; 99.79% based on the total amount of monomers used) of LIMA, 4.2 g (0.042 mol; 0.21% based on the total amount of monomers used) of methyl methacrylate, 39 g (1.95% based on the total amount of monomers used) of the chain transfer agent nDDM, and 29 g (1.45% based on the total amount of monomers used) of the chain transfer agent tDDM.

[0119] The mixture was charged to a 3-liter reactor equipped with a thermometer, temperature controller, addition funnel, purge gas inlet, and water-cooled reflux condenser with purge gas outlet, then inerted with dry ice (CO) and heated to 110°C in a nitrogen flow of 15 L / h with an agitator speed of 150 rpm. Once the reaction temperature was reached, a total of 20 g (1% based on the total amount of monomers used) of initiator solution (5 g; 0.25% based on the total amount of monomers used) in 15 g of LIMA was added in three steps: 2% of the initiator solution at 1 hour, 25% at 2 hours, and 73% at 3 hours. After all the initiator solution was charged, the mixture was given a 1-hour hold period.

[0120] Post-treatment of the polymer is described below.

[0121] Post-treatment of polymer solution 2 After a 1-hour hold period, the mixture was treated with initiator (4 g of tert-butyl peroxy-2-ethylhexanoate; 0.2% based on the total amount of monomers used). An additional 3-hour hold period followed. The mixture was then treated with another initiator shot (4 g of tert-butyl peroxy-2-ethylhexanoate; 0.2% based on the total amount of monomers used) and 10 g of additional monomer (2-ethylhexyl acrylate), immediately followed by the addition of the initiator. The mixture was stirred at reaction temperature overnight and added dropwise the next morning.

[0122] The process described yielded 2000 g (without additional monomer) or 2010 g (with additional monomer added) of polymer with a crude polymer solids content of 100%.

[0123] [Table 2]

[0124] Examples 1, 2, 7, and 8 are comparative examples because the process for producing these polymers did not involve adding a specific amount of additional monomer at the end of the polymerization reaction during post-treatment; only an additional initiator shot (chaser shot) was added.

[0125] Examples 3-6 and 9 are in accordance with the present invention because the methods for producing these polymers included an additional initiator shot at the end of the polymerization reaction, as well as the addition of EHA (Examples 3 and 4) or styrene (Examples 5 and 6) or LMA (Example 9).

[0126] The polyalkyl(meth)acrylate product produced according to the present invention contains 13% by weight methyl methacrylate and 87% by weight LMA.

[0127] [Table 3]

[0128] Examples 10-12 are comparative examples because the method for producing these polymers did not involve adding a specific amount of additional monomer at the end of the polymerization reaction during post-treatment; only an additional initiator shot was added.

[0129] Examples 13 and 14 are in accordance with the present invention because the process for preparing these monomers included an additional initiator shot at the end of the polymerization reaction, as well as the addition of EHA.

[0130] The polyalkyl(meth)acrylate product produced according to the present invention contains 0.21 wt.% methyl methacrylate and 99.79 wt.% LIMA.

[0131] The molecular weights and PDIs of the polymers produced according to the present invention are disclosed in Table 2 below.

[0132] [Table 4]

[0133] All examples have a very narrow range of weight average molecular weight M, from 53,600 g / mol (Example 9) to 54,600 g / mol (Examples 3 and 5) and 15,400 g / mol (Examples 13 and 14), respectively. w The PDI is 1.7 to 2.0.

[0134] [Table 5]

[0135] Examples 1-2 and 7-8 are comparative examples since no additional monomer was added in the post-treatment step. Examples 3-6 and 9 are in accordance with the invention since the process for their preparation included an additional initiator shot at the end of the polymerization reaction, as well as the addition of EHA (Examples 3 and 4) or styrene (Examples 5 and 6) or LMA (Example 9).

[0136] All kinematic viscosities measured at 100°C were 837 mm 2 / s (Example 2) and 913 mm 2 / s (Example 5), which means that all examples show approximately the same bulk viscosity.

[0137] The residual monomer contents of the Examples and Comparative Examples are listed in Table 4 below.

[0138] [Table 6]

[0139] Surprisingly, adding initiator at the end of polymerization was found to be more efficient when additional monomer was also added. The final residual monomer content of polyalkyl(meth)acrylates produced with an additional initiator shot and an additional monomer shot (Examples 3-6, 9, and 13-14) was lower than that produced without the addition of fresh monomer (Examples 1, 2, 7, and 8, and 10-12). This reduction was evident for total residual monomer as well as for individual monomers, here methyl methacrylate, and for the sum of long-chain (meth)acrylates or the sum of methacrylate and styrene.

[0140] The reduction in residual monomer content, as shown for each individual monomer, was in all cases more than 10% improved over the comparative example (see Figure 1).

[0141] The bulk viscosity (measured as KV100) and thickening efficiency of the product did not change significantly and were within the error range of reproducibility. The solids content generally increased slightly, making the method of producing the polymer product more economical.

[0142] A reduction in odor was also observed, along with the effect of the lower residual monomer content in the polyalkyl(meth)acrylates produced according to the present invention. These results are shown in Table 5 below.

[0143] [Table 7]

[0144] It can be concluded that the reduction in residual monomer content is accompanied by a reduction in odor.

[0145] The reduction of residual monomers in the product, especially methyl methacrylate, can be associated with an increase in flash point.

[0146] The calibration curve was determined using the Pensky-Martens closed cup flash point test according to ASTM D93, ISO 2719. Different polymer solutions A-E were prepared based on a polymer containing 87 wt% LMA and 13 wt% MMA (74% polymer in Chevron Group II base oil). Base polymer A was prepared by general polymerization procedure 1 as further described above, but without post-treatment.

[0147] Then, volatile compounds were removed from Polymer A using a rotary evaporator to obtain Polymer B.

[0148] To Polymer B were then added different amounts of MMA: about 0.1% gave Polymer C, about 0.4% gave Polymer D, and about 0.8% gave Polymer E.

[0149] The corresponding values ​​of residual monomer content are shown in Table 6 below.

[0150] [Table 8]

[0151] A clear correlation between the flash point and increasing residual MMA concentration was found, i.e., the flash point decreased with increasing residual MMA content. The correlation is visualized in Figure 4.

[0152] The residual LMA concentrations were nearly identical in Examples A-E.

Claims

1. 1. A method for producing a polyalkyl(meth)acrylate, comprising the steps of: (i) providing a reaction mixture, said reaction mixture comprising: (A) at least two different alkyl (meth)acrylates; (B) optionally, a chain transfer agent, and (C) optionally, a base oil and (ii) charging the reaction mixture provided in step (i) into a reaction vessel; (iii) heating the reaction mixture to a desired reaction temperature; (iv) adding, either continuously or stepwise, 0.1% to 4% by weight of free radical initiator 1, based on the total amount of monomers used; (v) after at least 95% monomer conversion has been achieved, adding to the reaction mixture 0.05% to 0.2% by weight of initiator 2, based on the total amount of monomers used, and less than 1% by weight, based on the total amount of monomers used, of an additional monomer selected from the group consisting of C4-14 alkyl acrylate, C4-14 alkyl methacrylate, C4-14 alkyl maleate, C4-14 alkyl fumarate, and styrene; (vi) optionally further processing the reaction mixture to obtain the target polyalkyl(meth)acrylate; Including, determining the conversion rate by measuring the residual monomer content by HPLC method; method.

2. The alkyl (meth)acrylate is, based on the total amount of the alkyl (meth)acrylate, (a) 0.2% to 50% by weight of a C1-6 alkyl (meth)acrylate; (b) 50% to 99.8% by weight of a C7-20 alkyl (meth)acrylate, and (c) 0% to 10% by weight of one or more additional comonomers 2. The method of claim 1, comprising:

3. The method of claim 2, wherein the C1-6 alkyl (meth)acrylate is methyl methacrylate.

4. The method according to claim 2 or 3, wherein the C7-20 alkyl (meth)acrylate is a C10-15 alkyl methacrylate.

5. 4. The method of claim 2 or 3, wherein the C7-20 alkyl (meth)acrylate is selected from linear or branched C10-15 alkyl methacrylates, and mixtures of linear and branched C10-15 alkyl methacrylates.

6. The method according to claim 2 or 3, wherein the C7-20 alkyl (meth)acrylate is lauryl methacrylate.

7. 2. The method of claim 1, wherein the chain transfer agent is selected from the group consisting of n-dodecyl mercaptan, tert-dodecyl mercaptan, 2-mercaptoethanol, and 2-ethylhexyl-thioglycolate.

8. 2. The method of claim 1, wherein initiator 1 and initiator 2 are independently selected from the group consisting of azo initiators and peroxy compounds.

9. The method of claim 1, wherein the additional monomer is selected from the group consisting of 2-ethylhexyl acrylate, lauryl methacrylate, and styrene.

10. The following steps (i) providing a reaction mixture, said reaction mixture comprising: (A) at least two different alkyl (meth)acrylates, (a) 0.2% to 25% by weight of a C1-6 alkyl (meth)acrylate, and (b) 75% to 99.8% by weight of a C7-20 alkyl (meth)acrylate at least two different alkyl (meth)acrylates comprising (B) optionally, a chain transfer agent, and (C) optionally, a base oil and (ii) charging the reaction mixture provided in step (i) into a reaction vessel; (iii) heating the reaction mixture to a desired reaction temperature; (iv) adding, either continuously or stepwise, 0.1% to 4% by weight of a free radical initiator 1, based on the total amount of monomers used; (v) after at least 95% monomer conversion has been achieved, adding to the reaction mixture 0.05% to 0.2% by weight of initiator 2, based on the total amount of monomers used, and less than 1% by weight, based on the total amount of monomers used, of an additional monomer selected from the group consisting of C4-14 alkyl acrylate, C4-14 alkyl methacrylate, C4-14 alkyl maleate, C4-14 alkyl fumarate, and styrene; (vi) optionally further processing the reaction mixture to obtain the target polyalkyl(meth)acrylate; Including, determining the conversion rate by measuring the residual monomer content by HPLC method; The method of claim 1.

11. The method of claim 1, wherein a polyalkyl(meth)acrylate is obtained having a total residual monomer content of less than 1% by weight, the residual monomer content being determined by an HPLC method.

12. The method of claim 1, wherein a polyalkyl(meth)acrylate is obtained having a residual methyl methacrylate content of less than 0.1% by weight, the residual monomer content being determined by HPLC.

13. 13. Use of the polyalkyl(meth)acrylates obtained by the process according to claim 11 or 12 as additives in industrial fluids.

14. (A) 0.5% to 50% by weight of a polyalkyl (meth)acrylate produced according to the method of claim 1; (B) 50% to 99.5% by weight of a base oil selected from the group consisting of API Group I, II, III, IV, and V oils, and mixtures thereof; (C) 0% to 5% by weight of one or more further additives; A method for producing an industrial fluid by mixing

15. (A) 0.5% to 25% by weight of a polyalkyl (meth)acrylate produced according to the method of claim 1; (B) 75% to 99.5% by weight of a base oil selected from the group consisting of hydrocarbon-based API Group I, II, III, IV, and V oils, and mixtures thereof; (C) 0% to 5% by weight of one or more further additives; A method for producing an industrial fluid by mixing

16. 16. The method of claim 14 or 15, wherein component (C) is selected from the group consisting of conventional VI improvers, dispersants, antifoam agents, detergents, antioxidants, pour point depressants, antiwear additives, extreme pressure additives, friction modifiers, corrosion inhibitors, dyes, and mixtures thereof.

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