Polyalkyl(meth)acrylate for improving lubricating oil properties

Abstract

The invention relates to a polyalkyl (meth) acrylate for improving lubricating oil properties, which comprises repetition units which are derived from (meth) acrylates having 6 to 22 carbon atoms in the alcohol residues, and repetition units which are derived from amine derivatives of an ethylenically unsaturated monomer. The invention further relates to methods for producing and using the present polyalkyl (meth) acrylate.

Claims

1. A polyalkyl(meth)acrylate being a graft copolymer, wherein: a graft base of the graft copolymer comprises: a) from 0 to 40% by weight of a repeat unit derived from a (meth)acrylate of formula (I) ##STR00005## b) from 20 to 99.9% by weight of a repeat unit derived from a (meth)acrylate of formula (II) ##STR00006## and c) from 0 to 20% by weight of a repeat unit derived from a (meth)acrylate of formula (III) ##STR00007## wherein each R is independently hydrogen or methyl, R.sup.1 is an alkyl radical having from 1 to 5 carbon atoms, R.sup.2 is an alkyl radical having from 6 to 22 carbon atoms, and R.sup.3 is an alkyl radical having from 23 to 4000 carbon atoms, and a graft of the graft copolymer comprises d) from 0.1 to 10% by weight of a repeat unit derived from an amine derivative of a polar ethylenically unsaturated monomer, wherein the polar ethylenically unsaturated monomer is maleic acid anhydride and the amine derivative is derived from N-phenyl-1,4-phenylenediamine.

2. The polyalkyl(meth)acrylate of claim 1, wherein the polyalkyl(meth)acrylate has a specific viscosity in the range from 5 to 35 ml/g at 100° C.

3. The polyalkyl(meth)acrylate of claim 1, comprising: a repeat unit derived from a styrene monomer.

4. The polyalkyl(meth)acrylate of claim 3, wherein the polyalkyl(meth)acrylate comprises 0.1 to 20% by weight of the repeat unit derived from a styrene monomer.

5. The polyalkyl(meth)acrylate of claim 1, comprising: a) from 0 to 40% by weight of a repeat unit derived from a (meth)acrylate of formula (I) ##STR00008## b) from 50 to 999% by weight of a repeat unit derived from a (meth)acrylate of formula (II) ##STR00009## c) from 0.5 to 20% by weight of a repeat unit derived from a (meth)acrylate of formula (III) ##STR00010## and d) from 0.1 to 10% by weight of a repeat unit derived from an amine derivative of a polar ethylenically unsaturated monomer, wherein each R is independently hydrogen or methyl, R.sup.1 is an alkyl radical having from 1 to 5 carbon atoms, R.sup.2 is an alkyl radical having from 6 to 22 carbon atoms, and R.sup.3 is an alkyl radical having from 23 to 4000 carbon atoms.

6. A process for preparing the polyalkyl(meth)acrylate of claim 1, the process comprising: preparing the graft base: subsequently grafting the polar ethylenically unsaturated monomer onto the graft base, and then reacting the resulting polymer with an amine.

7. The process of claim 6, wherein the polymerizing comprises: preparing a graft base by polymerizing the (meth)acrylate having from 6 to 22 carbon atoms, and subsequently grafting the polar ethylenically unsaturated monomer onto the graft base.

8. A lubricant composition comprising the polyalkyl(meth)acrylate of claim 1.

9. The lubricant composition of claim 8, comprising from 0.01 to 30% by weight of the polyalkyl(meth)acrylate.

10. A method of reducing friction, comprising: applying the composition of claim 8 to a composition or apparatus in need thereof.

11. The polyalkyl(meth)acrylate of claim 1, wherein the repeat unit derived from the (meth)acrylate of formula (III) comprises a polyolefin-based repeat unit having a number-average molecular weight of from 500 to 50,000 g/mol.

12. The polyalkyl(meth)acrylate of claim 5, wherein the repeat unit derived from the (meth)acrylate of formula (III) comprises a polyolefin-based repeat unit having a number-average molecular weight of from 500 to 50,000 g/mol.

Description

EXAMPLES AND COMPARATIVE EXAMPLES

Methods

(1) Determination of the Coefficient of Friction

(2) For measurements of the coefficient of friction, all polymers were diluted in Nexbase 3060 (an API group III base oil) to 3.5 mPas in HTHS150 according to ASTM D 4683. The coefficient of friction measurements were conducted on a mini traction machine from PCS Instruments under the following conditions:

(3) TABLE-US-00001 Test Rig MTM 2 from PCS Instruments Disk Steel, AISI 52100, diameter = 46 mm RMS = 25-30 nm, Rockwell C hardness = 63 Elastic modulus = 207 GPa Ball Steel, AISI 52100, diameter = 19.05 mm RMS = 10-13 nm, Rockwell C hardness = 58-65 Elastic modulus = 207 GPa Speed 5-2500 mm/s Temperature 100° C. Load 30N = max. Hertzian contact pressure 0.95 GPa. Slide/roll ratio 50%

(4) For evaluation, the area (integral) below the coefficient of friction curve determined for the candidate is expressed as a ratio to the area for the reference oil. The reference oil used is an API group III oil without addition of film-forming polymers and having an HTHS150 of 3.50 mPas. For the reference oil, the area was 64.5 mm*s.sup.−1 at 100° C.; see hatched area in FIG. 1. At 120° C., the area for the reference oil was only 45.96 mm*s.sup.−1.

(5) After determining the areas for the candidate oils, the reduction in the coefficient of friction can be calculated as follows:

(6) $\mathrm{Reduction}\mathrm{in}\mathrm{friction}\left(\mathrm{total}\right)=\frac{\begin{array}{c}{\int }_5^{2500}\mathrm{friction}\mathrm{values\_reference}\mathrm{oil}-\\ {\int }_5^{2500}\mathrm{friction}\mathrm{values\_candidate}\mathrm{oil}\end{array}}{{\int }_5^{2500}\mathrm{friction}\mathrm{values\_reference}\mathrm{oil}}*100\%$

(7) At high sliding speeds, the coefficient of friction is typically very small since the high speed results in a large amount of oil being introduced from the areas of friction into the lubrication gap. With decreasing sliding speed, less and less oil is introduced into the lubrication gap, and the coefficients of friction rise. It is of particular interest to lower the coefficients of friction, especially also at low sliding speeds. Therefore, not only is the reduction in friction based on the overall speed range (5-2500 mm/s) of interest, but also the reduction in friction at low sliding speeds (2-200 mm/s). The reduction in friction at low speeds is accordingly calculated as follows:

(8) $\mathrm{Reduction}\mathrm{in}\mathrm{friction}\left(\mathrm{low}\mathrm{speed}\right)=\frac{\begin{array}{c}{\int }_5^{200}\mathrm{friction}\mathrm{values\_reference}\mathrm{oil}-\\ {\int }_5^{200}\mathrm{friction}\mathrm{values\_candidate}\mathrm{oil}\end{array}}{{\int }_5^{200}\mathrm{friction}\mathrm{values\_reference}\mathrm{oil}}*100\%$
Wear Test on the 4-Ball Apparatus:

(9) The Shell four-ball apparatus (VKA) is a test instrument standardized in DIN 51 350 Part 1 for determination of the weld load and good load (DIN 51 350 Parts 2 and 3) and various friction and wear characteristics of lubricants (DIN 51 350 Parts 3 and 5). In the standard test, a rotating ball-bearing ball is pressed under load onto three identical but stationary balls. The test system is widespread in the lubricants industry in particular and is used routinely therein for product development and quality control.

(10) Wear is determined by visual measurement of the spherical caps formed. The mean is formed for the individually measured spherical cap diameters and for each load stage (150 N and 300 N). The end result reported is the sum of the two mean values, resulting from the mean spherical cap diameter at 150 N and 300 N.

(11) Polymer Characterization:

(12) To characterize the polymers, the specific viscosity was determined in an API group III base oil from Neste (NEXBASE 3060) at a fixed polymer concentration. The values determined are reported in the table shown below in ml/g.

(13) Polymer Synthesis

(14) General Synthesis Method of the Inventive Examples:

(15) The general synthesis method which follows was followed for all inventive polymers; the exact polymer composition, polymerization temperature and initiator content can be found in table 1.

(16) The monomers of the base polymer specified in table 1 were used to make up a mixture. All of the polymerization oil (=solvent in the polymerization) is initially charged in the reaction flask, which was equipped with internal temperature regulation, stirrer, nitrogen inlet and condenser. A sufficient amount of the monomer mixture was added to the initial charge in the reaction flask that oil and monomer mixture were present in a ratio of 9:1. Subsequently, while stirring and introducing nitrogen, the mixture was heated to reaction temperature. On attainment of the reaction temperature, the specified amount of initiator was fed in and the monomer feed was started.

(17) In some examples, a regulator (n-dodecyl mercaptan, nDDM) was used, which was added in the specified amount to the monomer mixture (only base polymer).

(18) The monomer feed consisted of the remaining monomer mixture with the specified amount of initiator in the feed. The feed was effected homogeneously over 3.5 hours. 2 hours after the feed had ended, another 0.2% initiator was optionally fed in at the specified reaction temperature.

(19) The mixture was kept at reaction temperature until at least 5 half-lives of the initiator had elapsed.

(20) In the case of performance of a graft polymerization, this was followed by heating to 130° C., addition of the specified amount of graft monomer and initiation of the graft reaction with 0.25% tert-butyl perbenzoate (tBPB). The amount of tBPB is based on the amount of base polymer plus the added graft monomer. 1 and 2 hours after commencement of the graft reaction, another 0.125% tBPB is fed in. After the last addition of initiator, the mixture is stirred at 130° C. for at least another 3 hours. The polymerizations of examples 1 to 9 shown in table 1 were graft polymerizations, the information in the square brackets describing the composition of the graft base.

(21) TABLE-US-00002 TABLE 1 Details of the preparation of the polymers used Composition Polymeri- of the Solids zation polymer content* nDDM temperature [% by wt.] [%] Initiator [%] [° C.] Example [pLMA-co-Sty- 70 tBPO 0.10 100 1 MMA]-g-MA 0.27% 86.3-9.7-1-3 Example [pLMA-co- 70 tBPO 0.05 110 2 EHMA]-g-MA 0.20% 68.4-30.1-1.5 Example [pLMA-co- 70 tBPO 0.19 110 3 MMA]-g-MA 0.24% 87.3-9.7-3 Example [pLMA-co-MMA- 55 tBPO — 90 4 Sty]-g-MA 0.35% 86.3-9.7-1-3 Example [pLMA-DPMA- 75 tBPO 0.30 110 5 SMA-MMA]-g-MA 3.7% 86.9-0.2- 0.2-9.7-3 Example [pLMA-co-MMA- 55 tBPO — 90 6 Sty-MA]-g-NVP 0.30% 80.7-8.2- 0.9-0.9-9.3 Example [pLMA-co-MMA- 70 tBPO — 100 7 Sty-MA]-g-MA 0.30% 94.1-1-1-1-2.9 Example [pLMA-co-MMA- 70 tBPO — 100 8 Sty-NVP]-g-MA 0.30% 94.1-1-1-1-2.9 Example [pLMA-co-MMA- 70 tBPO — 100 9 hPBDMA]-g-MA 0.20% 72-15-10-3 Example pLMA-co-GLMA 70 tBPO 0.90 100 10 95.9-4.1 0.25% Example pLMA-co-MMA- 50 tBPO — 100 11 Sty-MA 0.5% 87-6-6-1 Example pLMA-co-Sty- 50 tBPO — 100 12 MA 0.5% 87-6-1 Example pLMA-co-MMA- 50 tBPO — 100 13 MA 0.5% 87-12-1 *after polymerization

(22) The monomers used were abbreviated as follows: DPMA: alkyl methacrylate having 12 to 15 carbon atoms in the alkyl radical EHMA: ethylhexyl methacrylate GLMA: glycidyl methacrylate LMA: alkyl methacrylate having 12 to 14 carbon atoms in the alkyl radical MMA: methyl methacrylate MSA: maleic anhydride NVP: N-vinylpyrrolidone SMA: alkyl methacrylate having 16 to 18 carbon atoms in the alkyl radical Sty: styrene hPBDMA: macromonomer: methacrylate of a hydrogenated polybutadiene

(23) The resulting polymers were derivatized with an amine in a polymer-analogous reaction. The maleic anhydride (MA) or glycidyl methacrylate present in the polymers was reacted with the amines, N-phenyl-1,4-phenylenediamine (DPA) or N,N-dimethylaminopropylamine (DMAPA), listed in table 2 at about 140° C. The amine was added in equimolar amounts to MA or GLMA. The amine was either added in pure form or diluted in a suitable solvent. Preferred examples are butyl acetate or Plastomoll DNA. Any water formed was driven out by blowing in dry nitrogen. Volatile solvents such as butyl acetate, if any are used, have to be distilled off again under reduced pressure after the reaction. The inventive, fully converted polymers were diluted to the polymer content specified after the end of the reaction and optionally pressure-filtered through a depth filter layer. The amines used and the compositions obtained are shown in table 2.

(24) TABLE-US-00003 TABLE 2 Polymer content in end product ηsp/c 100° C. Amine [%] in NB 3060 Example 1 DPA 58.4 22.28 mL/g Example 2 DMAPA 60 24.88 mL/g Example 3 DPA 58.6 21.12 mL/g Example 4 DPA 50.6 23.40 mL/g Example 5 DPA 62.1  6.29 mL/g Example 6 DMAPA 40 not determined Example 7 DPA 50 not determined Example 8 DPA 50 not determined Example 9 DPA 45 28.98 Example 10 DPA 50 10.29 Example 11 DPA 48.6 14.48 Example 12 DPA 48.6 16.19 Example 13 DPA 48.6 15.61

(25) The above-detailed polymers of examples 1 to 5 which have been reacted with the amines according to table 2 were analyzed by the above methods. In addition, the viscosity index of lubricant oil compositions was determined, these data being described in table 3. The resulting values in relation to the improvement in coefficient of friction are shown in table 4. The measurements reported under reference relate to the base oil used.

(26) TABLE-US-00004 TABLE 3 Viscosity data KV40° C. KV100° C. Formulation [mm.sup.2/s] [mm.sup.2/s] VI Example 1 8.0% in Nexbase 66.42 13.20 205 3060 Example 2 7.65% in 68.80 13.01 193 Nexbase 3060 Example 3 8.6% in Nexbase 67.80 13.34 203 3060 Example 4 8.15% in 44.08 9.86 203 Nexbase 3060 Example 5 20.7% in 67.12 11.48 166 Nexbase 3060 Example 7 9.6% in RMF 5/2 95.06 16.39 186 (150N oil) Example 8 9.6% in RMF 5/2 111.1 18.68 189 (150N oil) Example 9 10.67% in RMF 101.7 20.39 226 5/2 (150N oil) Example 10 13.5% in 60.57 11.57 189 Nexbase 3060 Example 11 11.8% in 57.59 11.13 190 Nexbase 3060 Example 12 10.6% in 58.58 11.07 185 Nexbase 3060 Example 13 11% in Nexbase 55.31 11.12 199 3060 Nexbase 3060 is a commercially available group III oil RMF 5/2 is a commercial 150N oil

(27) In addition, the inventive lubricants exhibit an excellent high-shear viscosity HTHS measured at 150° C., with values determined for some examples in the range from 3.19 (example 12) to 3.83 (example 5).

(28) TABLE-US-00005 TABLE 4 Coefficients of friction Low- Improvement Improvement Total speed in friction in friction Low area area Total in % speed in % Reference 64.51 9.25 0.0 0.0 Example 1 53.83 5.02 16.6 45.7 Example 2 61.40 6.91 4.8 25.3 Example 3 54.58 5.47 15.4 40.9 Example 4 52.29 4.92 18.9 46.8 Example 5 55.07 5.16 14.6 44.2

(29) The results in table 4 show clearly that the inventive polymers lead to a distinct decrease in the coefficients of friction. Particularly in the region of the low sliding speeds, which often occur in real applications and are therefore of particular interest, reductions in the coefficient of friction of more than 50% are achievable.

(30) The results also show that styrene-containing polymers exhibit better friction characteristics than the corresponding styrene-free products. Even small amounts of styrene of, for example, 1% show a distinct effect; compare example 4 (1% styrene) with examples 2 and 3 (no styrene).

(31) In addition, the compatibility of the inventive polymers with commercial PIB succinimides (Infineum C9201) was studied.

(32) For this purpose, 1% by weight (active substance) of a commercial PIB succinimide (Infineum C9201) was added. The coefficient of friction measurements were conducted and evaluated as described above, but the measurement temperature was 120° C. The results of the evaluation are summarized in table 5.

(33) TABLE-US-00006 TABLE 5 Coefficients of friction with and without addition of PIB succinimide Low-speed Total area area Low-speed without without Total area area with PIBSI PIBSI with PIBSI PIBSI Reference 45.96 8.43 45.96 8.43 Example 5 41.75 6.06 42.62 5.98

(34) The results show that the present copolymer essentially retains the excellent improvement in coefficient of friction, even in the case of addition of PIBSI, and a slight improvement therein can be measured in the low-speed range.

(35) In addition, the wear characteristics were determined in a fully formulated oil with addition of a commercially available ashless antiwear package. In this case, the inventive polymer according to example 1 was diluted to a KV100 of 9.50 mm.sup.2/s in a mixture of APE Core 80N:APE Core 150N=70:30. The oil contained about 0.90% by weight of the ashless antiwear package mentioned. The results of the wear test are shown in table 6. If a spherical cap diameter of 0.00 mm is reported as the result, no spherical cap was visible on the ball (=no wear, only negligible, unmeasurable plastic deformation). The oil was determined twice for each load stage:

(36) TABLE-US-00007 TABLE 6 Wear data Polymer according to example 1 Load 150N 300N Ball 1 0.00/0.00 0.10/0.10 Ball 2 0.00/0.00 0.00/0.00 Ball 3 0.00/0.00 0.00/0.00 Ball 4 0.00/0.00 0.00/0.00 Ball 5 0.00/0.00 0.00/0.00 Ball 6 0.00/0.00 0.00/0.00 Average 0.00/0.00 0.017/0.017 Result 0.00 0.034 Sum 0.03 mm