HK1076121A - Hnbr compounds having an improved flowability - Google Patents

Description

Hydrogenated nitrile rubber compound with improved flowability

Technical Field

The present invention relates to a composition with improved flowability comprising at least one hydrogenated nitrile rubber, a process for improving the flowability of a composition comprising at least one hydrogenated nitrile rubber and a process for improving the fluid aging of a composition comprising at least one hydrogenated nitrile rubber.

Background

Hydrogenated nitrile rubber (HNBR), prepared by selective hydrogenation of acrylonitrile-butadiene rubber (nitrile rubber; NBR, a copolymer comprising at least one conjugated diene, at least one unsaturated nitrile and optionally further comonomers), is a specialty rubber with very good heat resistance, excellent ozone and chemical resistance and excellent oil resistance. In addition to the high level of mechanical properties (in particular high abrasion resistance) of the rubber, it is not surprising to find wide use in the automotive industry (seals, hoses, bearing pads), the petroleum industry (stators, well head seals, valve plates), the electrical industry (cable sheathing), the mechanical engineering industry (wheels, rollers) and the shipbuilding industry (gland pipes, connectors) and in other industries.

The commercially available HNBR has a Mooney viscosity in the range of 55 to 105, a molecular weight in the range of 200,000 to 500,000g/mol, a polydispersity greater than 3.0 and a Residual Double Bond (RDB) content in the range of 1 to 18% (determined by infrared spectroscopy).

One limitation in processing HNBR is the relatively high mooney viscosity. In principle, HNBR having a low molecular weight and a low Mooney viscosity would have better processability. Attempts have been made to reduce the molecular weight of polymers by mastication (mechanical breakdown) and by chemical means (e.g., using strong acids), but these methods have the disadvantage of leading to the introduction of functional groups (such as carboxylic acid and ester groups) into the polymer and altering the microstructure of the polymer. These disadvantages lead to an unfavorable change in the properties of the polymer.

GB-A-2,019,413 discloses rubber compositions comprising organosiloxanes having hydrocarbon groups with more than 4 carbon atoms. However, hydrogenated nitrile rubbers and organosiloxanes having at least one hydrocarbon group of less than 4 carbon atoms are not disclosed and the teachings of this reference are limited to improving thermal stability.

US-3,332,900 discloses adducts of siloxanes and isocyanates. However, hydrogenated nitrile rubbers are not disclosed.

EP-A-0045641 discloses vinyl resin compositions comprising organosiloxanes. However, hydrogenated nitrile rubbers are not mentioned.

US-3,450,736 discloses modified silicone polymers and compositions containing the above silicone polymers. However, hydrogenated nitrile rubbers are not disclosed.

EP-A-0243514 discloses ｃA process for producing rubber compositions comprising organosiloxanes as processing aids. However, hydrogenated nitrile rubbers are not disclosed.

Disclosure of Invention

The present invention provides a composition with improved flowability comprising at least one hydrogenated nitrile rubber and at least one organopolysiloxane having at least one hydrocarbon group of less than 4 carbon atoms. The present invention also provides a process for improving the flowability of a composition comprising at least one hydrogenated nitrile rubber by adding to said composition at least one organopolysiloxane having at least one hydrocarbon group of less than 4 carbon atoms. Further, the present invention provides a method for improving the fluid aging of a composition comprising at least one hydrogenated nitrile rubber by adding to said composition at least one organopolysiloxane having at least one hydrocarbon group of less than 4 carbon atoms.

Detailed Description

The term "nitrile rubber" or NBR as used throughout the specification has a broad meaning and includes copolymers comprising repeat units from at least one conjugated diene, at least one α, β -unsaturated nitrile, and optionally one or more other copolymerizable monomers.

Hydrogenated Nitrile Butadiene Rubber (HNBR) in the present invention is understood to be nitrile butadiene rubber/NBR in which more than 50% of the Residual Double Bonds (RDB) are hydrogenated, preferably more than 90% of the RDB are hydrogenated, more preferably more than 95% of the RDB are hydrogenated and most preferably more than 99% of the RDB are hydrogenated.

The conjugated diene may be any known conjugated diene, in particular C₄-C₆A conjugated diene. Preferred conjugated dienes are butadiene, isoprene, piperylene, 2, 3-dimethylbutadiene and mixtures thereof. More preferred is C₄-C₆The conjugated diene is butadiene, isoprene and mixtures thereof. Most preferred C₄-C₆The conjugated diene is butadiene.

The alpha, beta-unsaturated nitrile may be any of the known alpha, beta-unsaturated nitriles, especially C₃-C₅An α, β -unsaturated nitrile. Preferred is C₃-C₅The α, β -unsaturated nitriles are acrylonitrile, methacrylonitrile, ethacrylonitrile, and mixtures thereof. Most preferred C₃-C₅The α, β -unsaturated nitrile is acrylonitrile.

Preferably, the copolymer comprises in the range of from 40 to 85 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 15 to 60 weight percent of repeating units derived from one or more unsaturated nitriles. More preferably, the copolymer comprises in the range of from 60 to 75 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 25 to 40 weight percent of repeating units derived from one or more unsaturated nitriles. Most preferably, the copolymer comprises in the range of from 60 to 70 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 30 to 40 weight percent of repeating units derived from one or more unsaturated nitriles.

Optionally, the copolymer may further comprise repeating units derived from one or more copolymerizable monomers, such as unsaturated carboxylic acids. Non-limiting examples of suitable unsaturated carboxylic acids are fumaric acid, maleic acid, acrylic acid, methacrylic acid and mixtures thereof. Repeating units from one or more copolymerizable monomers may replace the nitrile or diene portion of the nitrile rubber and it will be apparent to those skilled in the art that the above mentioned numbers may be adjusted to yield 100 weight percent. In the case of the unsaturated carboxylic acids mentioned, the nitrile rubbers preferably contain repeating units from one or more unsaturated carboxylic acids in the range from 1 to 10 percent by weight of the rubber, the repeating units having a number substituted for the corresponding number of conjugated dienes.

Other preferred optional additional monomers are unsaturated mono-or dicarboxylic acids or their derivatives (e.g., esters, amides, etc.), including mixtures thereof.

Examples of suitable HNBRs include Therban * a3407, Therban * C3467 or Therban * a3907, all of which are available from Bayer inc.

HNBR can be used alone or in combination with other elastomers, such as:

BR-polybutadiene

ABR-butadiene/acrylic acid C₁-C₄Alkyl ester copolymers

CR-polychloroprene

IR-polyisoprene

SBR-styrene/butadiene copolymers having a styrene content of from 1 to 60, preferably from 20 to 50,% by weight

IIR-isobutylene/isoprene copolymer

NBR-butadiene/acrylonitrile copolymers having an acrylonitrile content of 5 to 60, preferably 10 to 40 wt.%

EPDM-ethylene/propylene/diene copolymer

The organopolysiloxane may be any known organopolysiloxane having at least one hydrocarbon group of less than 4 carbon atoms, preferably all hydrocarbon groups of less than 4 carbon atoms. Preferred organopolysiloxanes have the general structure (I)

R₂R’SiO-(RR’SiO)_m-(R”₂SiO)_n-SiR’R₂ (I)

Wherein R and R' can be the same or different and are independently a substituted or unsubstituted monovalent hydrocarbon radical having from 1 to 3 carbon atoms and m/n is less than or equal to 1, specifically less than or equal to 0.1, more specifically less than or equal to 0.01. More preferably, the organopolysiloxane may be a cyclic or linear structure without crosslinking between chains. Preferred R and R' and R "are selected from the group consisting of methyl, ethyl, propyl, vinyl. More preferably, the organopolysiloxane is Polydimethylsiloxane (PDMS) having the general structure (I) wherein R and R "are methyl groups and R' is an organic substituent having less than 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, vinyl. The viscosity of the organopolysiloxane is not critical, preferably the viscosity has a range of 500 to 250000 mpa.s.

Suitable organopolysiloxanes include PS447^TMA vinyldimethyl-terminated polydimethylsiloxane from integrated Technology (United Technology). PS047^TMA trimethyl endblocked polydimethylsiloxane from united technology (unitedttechnology). Silopren^TMU1 and U165, vinyldimethyl-terminated polydimethylsiloxane from GE-Bayer Silicones.

The composition of the present invention may vary over a wide range. Preferably, the composition comprises in the range of from 1 to 20phr of organopolysiloxane, more preferably from 1 to 10phr, most preferably from 3 to 7 phr.

The composition may also comprise one or more fillers.

The filler may be a non-mineral or mineral filler. Examples of mineral fillers include silica, silicates, clays (e.g., bentonite), gypsum, alumina, titanium dioxide, talc, and the like, including mixtures thereof.

Further examples are:

highly dispersible silicas, such as those prepared by precipitation of silicate solutions or flame hydrolysis of silicon halides, having a size ranging from 5 to 1000, preferably from 20 to 400m²A specific surface area (BET specific surface area) of/g, and having a primary particle size of 10 to 400 nm; the silica can also optionally be present as mixed oxides with other metal oxides, such as oxides with aluminum, magnesium, calcium, barium, zinc, zirconium and titanium;

synthetic silicates such as aluminum silicate and alkaline earth metal silicate, etc.;

-has 20 to 400m²A BET specific surface area in the range of/g and magnesium or calcium silicate having a primary particle diameter of from 10 to 400 nm;

natural silicates such as kaolin and other naturally occurring silicas;

glass fibers and glass fiber products (mat, extrudate) or glass microspheres;

metal oxides, such as zinc oxide, calcium oxide, magnesium oxide and aluminum oxide;

metal carbonates, such as magnesium carbonate, calcium carbonate and zinc carbonate;

metal hydroxides, such as aluminum hydroxide and magnesium hydroxide;

or a combination thereof.

Suitable silica fillers are available from PPG Industries Inc (PPG Industries Inc.) under the trademarks HiSil * 210, HiSil * 233, and HiSil * 243. Vulkasil * S and Vulkasil * N from Bayer AG are also suitable as fillers.

The non-mineral filler may be a carbon black such as carbon black prepared by lamp black, furnace black or gas black processes, such as SAF, ISAF, HAF, FEF or GPF carbon black.

Optionally, the rubber composition of the present invention further comprises a carbodiimide, a polycarbodiimide, or a mixture thereof. A preferred carbodiimide is commercially available under the trademark Rhenogram^TMP50 and Stabaxol^TMAnd (5) P variety. This component may be used in the rubber composition of the present invention in an amount ranging from 0 to about 15 parts by weight, more preferably from 0 to about 10 parts by weight, and even more preferably from about 0 to about 2 parts by weight.

Optionally, the rubber composition of the present invention further comprises an acrylate compound. The term "acrylate compound" as used throughout the specification has a broad meaning and includes compounds having the general structure [ R-CH ═ CR' COO^-]_nMⁿ⁺Wherein R and R' are independently selected aliphatic or aromatic hydrocarbon groups or hydrogen, and are the same or different from each other, and M is a metal ion selected from group 2, 12 or 13 (IUPAC1985), and n is an integer of 2 or 3, and liquid acrylates such as trimethylolpropane Trimethacrylate (TRIM), Butanediol Dimethacrylate (BDMA) and ethylene glycol dimethacrylate (EDMA). Detailed descriptions of acrylates are known from EP-A1-0319320, in particular on page 3, lines 16 to 35, from US-5208294, in particular on column 2, lines 25 to 40, and from US-4983678, in particular on column 2, lines 45 to 62. Preference is given to zinc acrylate, zinc diacrylate or zinc dimethacrylate or a liquid acrylate. It may be advantageous to use a combination of different acrylates and/or their metal salts.

In the rubber composition of the present invention, the amount of the acrylic compound is in the range of 0 to 100phr (parts per 100 parts of rubber), preferably 0.1 to 20phr, more preferably 0.2 to 7 phr.

The rubber composition of the present invention may contain one or more vulcanizing agents or vulcanizing systems. The present invention is not limited to a particular curing system, however, peroxide curing systems are preferred. Furthermore, the present invention is not limited to a particular peroxide cure system. For example, inorganic or organic peroxides are suitable. Preferred are organic peroxides such as dialkyl peroxides, ketal peroxides, aralkyl peroxides, peroxy ethers, peroxy esters such as di-tert-butyl peroxide, bis- (tert-butylperoxyisopropyl) -benzene, dicumyl peroxide, 2, 5-dimethyl-2, 5-di (tert-butylperoxy) -hexane, 2, 5-dimethyl-2, 5-di (tert-butylperoxy) -hexene- (3), 1-bis (tert-butylperoxy) -3,3, 5-trimethylcyclohexane, benzoyl peroxide, tert-butylcumyl peroxide and tert-butyl perbenzoate. Conventional amounts of peroxide in the composition range from 1 to 10phr, preferably from 4 to 8 phr. The subsequent vulcanization is generally carried out at a temperature in the range from 100 to 200 ℃ and preferably in the range from 130 to 180 ℃. Peroxides can be effectively used in a manner that combines with polymers. Suitable systems are commercially available, such as Polydispersion T (VC) D-40P, D (polymer-bound di-T-butylperoxycumene) from Rhein Chemie Rheinau GmbH.

The rubber composition according to the invention may contain further auxiliary materials for rubbers, such as reaction accelerators, vulcanization acceleration auxiliary materials, antioxidants, foaming agents, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, plasticizers, binders, foaming agents, colorants, pigments, waxes, extenders, organic acids, inhibitors, metal oxides and activators such as triethanolamine, polyethylene glycol, hexanetriol, etc., which are known to the rubber industry. The rubber auxiliaries are used in conventional amounts, depending inter alia on the intended use. Customary amounts are, for example, from 0.1 to 50 phr. Preferably the vulcanizable compound comprises said rubber compound, further comprising in the range of 0.1 to 20phr of one or more organic fatty acids as adjuvants, preferably unsaturated fatty acids having 1, 2 or more carbon double bonds in the molecule, wherein more preferably 10% by weight or more of conjugated diene acids having at least one conjugated carbon-carbon double bond in the molecule are comprised. Preferred fatty acids have from 8 to 22 carbon atoms, more preferably from 12 to 18 carbon atoms. Examples include stearic acid, palmitic acid and oleic acid and their calcium, zinc, magnesium, potassium and ammonium salts.

The components of the rubber composition are typically blended together, suitably at elevated temperatures in the range of from 25 ℃ to 200 ℃. Generally, a mixing time of not more than 1 hour and a time in the range of 2 to 30 minutes is usually sufficient. The mixing of the rubber and organopolysiloxane, optional filler, optional vulcanizing agent, and/or other components is suitably carried out in an internal mixer such as a Banbury mixer (Banbury mixer) or a Haake (Haake) or Brabender internal mixer. The two roll mill mixer also provides excellent dispersion of the compounds in the final product. The extruder also provides good mixing and enables shorter mixing times. The mixing can be carried out in two or more stages and can be carried out in different apparatuses, for example one stage in an internal mixer and another stage in an extruder. However, care should be taken during the mixing stage that no unwanted pre-crosslinking (═ scorch) should occur. Also visible with respect to mixing and vulcanization are: encyclopedia of Polymer Science and engineering (Encyclopedia of Polymer Science and engineering) Vol 4, pp 66 et seq (mixtures) and the following, and Vol 17, pp 666 et seq (vulcanization).

The rubber composition is ideally suited for, but not limited to, processing by injection molding processes. The rubber composition can also be used for transfer molding, compression molding, liquid injection molding. The rubber composition comprising the crosslinking system is typically injected into a conventional injection molding machine and into a heated (about 160-230 ℃) molding mold, wherein crosslinking/vulcanization occurs depending on the temperature of the rubber composition and mold.

The rubber composition is well suited for the manufacture of shaped products such as seals, hoses, bearing pads, stators, well head seals, valve plates, cable sheathing, wheel mills, gland pipes, gaskets in place or shoe parts. Furthermore, they are well suited for the production of wires and cables.

The rubber composition provides improved flow and better molding characteristics during processing such as injection molding, extrusion molding, compression molding. This improved processability results in increased flow rates, resulting in parts with sharp edges and smooth surfaces. Furthermore, the fluid aging properties are improved relative to the extractable plasticizer.

The invention is further illustrated in the following examples.

Detailed Description

Examples

Description of the experiments

Mooney viscosity was determined according to ASTM D1646. MDR was determined according to D5289. Stress strain and fluid aging were determined from D412 and D471, respectively. Capillary rheometry was performed with a Monsanto Process usability Tester (MPT). The process is technically equivalent to method A in ASTM D-5099-93, except for the capillary die specifications (tube inner diameter: 19mm, tube length: 25.4 mm).

Examples 1 to 7

Conventional blend formulation:

in a separate mixing step, the compounds were mixed on an open mill using standard laboratory mixing procedures (40 ℃, 10 minutes mixing). The formulations used in this evaluation were based on a simplified peroxide formulation (table 1).

TABLE 1 blend formula

Component Phr

Therban*^* 100

Carbon black, N66050

Plasticizer^* 0-10^*

Maglite*D 2

Naugard*445 1

Vulkanox*ZMB-2/C5(ZMMBI) 0.5

Zinc oxide (Kadox * 920) Grade PC 2163

DIAK*#7 1.5

Vulcup*40KE 7.5

^*For detailed information, please refer to Table 2

Carbon Black N660 Sterling-V from Cabot fire Blacks

Maglite * D is a magnesium oxide (MgO) from c.p. hall.

Naugard * 445 is a diphenylamine available from Uniroyal Chemical.

Plasthall * TOTM is a trioctyl trimellitate from c.p.

Vulkanox * ZMB-2/C5 is a zinc salt of 4-and 5-methyl-mercaptobenzimidazole from Bayer AG

DIAK #7 is a triallyl isocyanurate from Dupont Dow Elastomers

Vulcup 40KE is 2, 2' -bis (tert-butyl diisopropylbenzene peroxide) from hartick Standard.

TABLE 2 detailed compounding recipe for each example

Examples	Therban*	Plasticizer
			1*(control)	Therban*A3406	5phr of Plasthall * TOTM
2*(control)	Therban*A3406	5phr of Struktol * WB-222
			3	Therban*A3406	5phr of PS447 *
4	Therban*A3406	5phr of Silopren * U5
			5	Therban*A3406	5phr of Silopren * U65
6	Therban*A3406	5phr of Silopren * U165
			7	Therban*A3406	5phr of PS047 *

^*Examples 1 and 2 as controls

PS 447^TMA vinyldimethyl-terminated polydimethylsiloxane from United technology; PS047^TMA trimethyl endblocked polydimethylsiloxane from unitedttechnology; silopren^TMU5, U65 and U165, vinyldimethyl-terminated polydimethylsiloxane from GE-Bayer Silicones; struktol * WB 222 is a processing additive from Struktol corporation (Struktol Company).

Results

The properties of the compositions of examples 1-7 were tested. The results are listed in table 3.

Discussion of the related Art

The physical properties (measured by stress strain) of the compositions 3 to 7 according to the invention are comparable to those of the comparative example 1^*And 2^*The physical properties of (a). Compositions 3-7 exhibited similar flow as determined by capillary rheology. The tubing pressure of the control example was approximately 1.8 times higher than the composition of the present invention. The results of fluid aging after 168 hours at 150 ℃ in ASTM Oil #1 and IRM903 show that extraction of TOTM from the polymer matrix in Oil #1 using a soluble low molecular weight plasticizer such as Plasthall TOTM results in a weight loss of approximately 2% (5phr of TOTM calculated to be 2.8%). In comparison, the control mixture, in which no plasticizer was added to the formulation, showed a small positive weight change.

On the other hand, the polysiloxane additives showed an increase in weight of about 1%, indicating that they were not extracted from the polymer matrix.

TABLE 3

Example 1^* 2^* 3 4 5 6 7

Compound Mooney viscosity 82.776.687.489.486.087.888.9

ML1+4@100℃

MDR vulcanization Properties

1.7Hz, 1 degree radian, 180 ℃, 30min, 100dNm

MH(dN.m) 50.9 49.0 54.3 54.8 54.3 54.2 53.5

ML(dN.m) 2.4 2.5 2.8 3.0 2.8 2.9 2.8

ΔMH-ML(dN.m) 48.5 46.5 51.5 51.9 51.5 51.3 50.7

Stress strain (dumbbell)

Vulcanization time @180 ℃ (min) 13121212121212

Ultimate tensile strength (MPa) 24.726.023.624.125.225.223.2

Ultimate elongation (%) 254283230233223225219

Shore A2 type hardness (pts.) 65686768686867

Aging at 150 ℃ for 168h in ASTM Oil #1

Shore A2 type hardness (pts.) 67686767686869

Ultimate tensile strength (MPa) 24.825.026.225.123.725.225.6

Ultimate elongation (%) 211218214204179199203

Shore A2 hardness Change (pts.) 200-1002

The change rate of ultimate tensile strength (%) is 1 to 4% 11 to 6% and 0 to 10%

The percent change of ultimate elongation is-17% -23% -7% -12% -20% -12% -7%

Weight change rate (%) -2.0-1.31.11.11.11.01.0

Volume change rate (%) -2.1-131.61.41.51.31.0

Aging in IRM903 at 150 deg.C for 168h

Shore A2 type hardness (pts.) 60546162626161

Ultimate tensile strength (MPa) 21.519.720.015.618.920.017.9

Ultimate elongation (%) 209199174152172178169

Shore A2 type hardness Change (pts.) 5-14-6-6-6-7-6

The percent change of the ultimate tensile strength (%) -13% -24% -15% -35% -25% -21% -23%

The percent change of ultimate elongation is 18 percent to 30 percent to 24 percent to 35 percent to 23 percent to 21 percent to 23 percent

Weight change rate (%) 12.113.615.916.416.016.316.3

Volume change rate (%) 14.916.519.419.919.519.719.4

Capillary rheometry @100 deg.C

Pressure @28.9s^-1(psi) 5610 1010 1400 1200 1350 1390 1360

Pressure @101.2s^-1(psi) 7220 3230 2170 1720 2120 2190 2050

Pressure @300s^-1(psi) 7610 5350 3140 2730 3170 3220 3090

Pressure @10013s^-1(psi) 8910 8910 4900 4770 4910 4900 4810

Pressure @3005.6s^-1(psi) 8660 N.Aa 8470 8800 8710 8390 8520

Pressure @9991.2s^-1(psi) 13730 12990 N.Aa N.Aa 12910 13260

^aExceeds the upper limit of the equipment

Claims (10)

1. A composition comprising at least one hydrogenated nitrile rubber and at least one organopolysiloxane having at least one hydrocarbon group of less than 4 carbon atoms.

2. A composition according to claim 1 wherein the organopolysiloxane has at least one hydrocarbon group of less than 4 carbon atoms and has the general structure (I)

R”₂R’SiO-(R”R’SiO)_m-(R”₂SiO)_n-SiRR”₂ (I)

Wherein R and R' can be the same or different and are independently a substituted or unsubstituted monovalent hydrocarbon radical having in the range of 1 to 3 carbon atoms and m/n is equal to or less than 1.

3. A composition according to claim 2, wherein the organopolysiloxane is Polydimethylsiloxane (PDMS).

4. A composition according to any one of claims 1 to 3, wherein the hydrogenated nitrile rubber comprises repeating units derived from at least one conjugated diene, at least one α, β -unsaturated nitrile and optionally one or more other copolymerizable monomers.

5. A composition according to any one of claims 1 to 4 further comprising one or more fillers and/or one or more vulcanizing agents or systems.

6. A composition according to any one of claims 1 to 5 having improved flowability.

7. A composition according to any one of claims 1 to 5 having improved resistance to fluid ageing.

8. A method for improving the flow properties of a composition comprising at least one hydrogenated nitrile rubber, comprising adding to said composition at least one organopolysiloxane having at least one hydrocarbon group of less than 4 carbon atoms.

9. A method for improving the fluid aging of a composition comprising at least one hydrogenated nitrile rubber comprising adding to said composition at least one organopolysiloxane having at least one hydrocarbon group of less than 4 carbon atoms.

10. A process for the manufacture of shaped products, wherein a composition according to any one of claims 1 to 7 is used for injection moulding, extrusion moulding or compression moulding.