HK1075264A - Butyl compositions comprising nitrile polymers - Google Patents

Description

Butyl rubber composition comprising nitrile polymer

Technical Field

The present invention relates to a polymer composite comprising at least one, optionally hydrogenated, carboxylated nitrile rubber polymer, and at least halogenated butyl rubber; a process for preparing said polymer composite, wherein at least one optionally hydrogenated carboxylated nitrile rubber polymer and at least halogenated butyl rubber are mixed; a shaped article comprises at least one optionally hydrogenated carboxylated nitrile rubber polymer and at least halogenated butyl rubber.

Background

The physical properties of vulcanizates are greatly influenced by the crosslink density.

Hydrogenated nitrile rubber (HNBR), which is prepared from selectively hydrogenated acrylonitrile-butadiene rubber (nitrile rubber; NBR, which is a copolymer comprising at least one conjugated diene, at least one unsaturated nitrile and optionally further comonomers), is a specialty rubber which has good heat resistance, excellent ozone and chemical resistance properties, and excellent oil resistance. With the high level of mechanical properties of the rubber, in particular high abrasion resistance, it has not surprisingly been found that NBR and HNBR have wide applications in the automotive (seals, hoses, bearing pads), petroleum (baffles, well head seals, valve plates), electrical (cable sheathing), mechanical engineering (wheels, rollers) and shipbuilding (pipe seals, couplings) industries and other industries. Hydrogenated carboxylated nitrile rubber polymers (HXNBR) have been disclosed in WO-01/77185-A1.

Halogenated butyl rubbers are commercially available from Bayer Inc (Bayer corporation).

Disclosure of Invention

In one aspect, the present invention relates to a polymer composite comprising at least one, optionally hydrogenated, carboxylated nitrile rubber polymer and at least a halogenated butyl rubber. Preferably the optionally hydrogenated carboxylated nitrile rubber polymer is a statistically distributed copolymer. It is further preferred that the halogenated butyl rubber is a brominated butyl rubber or "bromobutyl" rubber. Preferably, the carboxylated nitrile rubber polymer ("XNBH") is fully or partially hydrogenated ("HXNBR").

In another aspect, the invention relates to a process for preparing said polymer composite comprising at least one optionally hydrogenated carboxylated nitrile rubber polymer and at least halogenated butyl rubber, wherein said at least one optionally hydrogenated carboxylated nitrile rubber polymer and at least halogenated butyl rubber are mixed.

In a further aspect the present invention relates to a shaped article comprising at least one, optionally hydrogenated, carboxylated nitrile rubber polymer and at least a halogenated butyl rubber.

In yet another aspect, the invention relates to a process for increasing the crosslink density of halogenated butyl rubber by mixing said halogenated butyl rubber with at least one optionally hydrogenated carboxylated nitrile rubber polymer, optionally at least one crosslinking agent and optionally a filler, and then curing the compound.

Drawings

FIG. 1 shows the torque (MH) in dN.m at 1 radian of twist and 170 ℃ after the first hour of vulcanization of the mixtures of examples 1-3.

Detailed Description

The term "nitrile polymer" or XNBR as used throughout the specification has a broad meaning and is meant to include copolymers having repeat units derived from at least one conjugated diene, at least one alpha-beta-unsaturated nitrile, at least one monomer having a carboxyl group and optionally one or more other copolymerizable monomers.

The conjugated diene may be any known conjugated diene, in particular C₄-C₆The conjugated diene of (1). Preferred conjugated dienes are butadiene, isoprene, 1, 3-pentadiene, 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, in particular C₃-C₅Of (a) is an alpha-beta-unsaturated nitrile. Preferred is C₃-C₅The alpha-beta-unsaturated nitriles of (a) are acrylonitrile, methacrylonitrile, ethacrylonitrile and mixtures thereof. Most preferred C₃-C₅The alpha-beta-unsaturated nitrile of (a) is acrylonitrile.

The monomer having at least one carboxyl group may be any known monomer having at least one carboxyl group and copolymerizable with the nitrile and the diene.

Preferably, the monomer having at least one carboxyl group is an unsaturated carboxylic acid. Non-limiting examples of suitable unsaturated carboxylic acids are fumaric acid, maleic acid, acrylic acid, methacrylic acid and mixtures thereof. Other preferred monomers are unsaturated mono-or dicarboxylic acids or derivatives thereof (e.g., esters, amides, etc.) including mixtures thereof. Preferably the copolymer comprises from 40 to 85 wt% repeating units derived from one or more conjugated dienes, from 15 to 60 wt% repeating units derived from one or more unsaturated nitriles and from 0.1 to 15 wt% repeating units derived from one or more monomers having at least one carboxyl group. More preferably, the copolymer comprises from 55 to 75 weight percent of repeating units derived from one or more conjugated dienes, from 25 to 40 weight percent of repeating units derived from one or more unsaturated nitriles and from 1 to 7 weight percent of repeating units derived from one or more monomers having at least one carboxyl group.

The copolymer may optionally further comprise repeating units derived from one or more copolymerizable monomers, such as alkyl acrylates, styrene. Repeating units derived 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 numbers are adjusted to meet 100 wt%.

Hydrogenation in the present invention is preferably understood to mean that more than 50% of the Residual Double Bonds (RDB) in the starting nitrile polymer/NBR 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 present invention is not limited to a particular process for preparing hydrogenated carboxylated nitrile rubber. However, the HXNBR preferred in the present invention has been obtained as disclosed in WO-01/77185-A1. WO-01/77185-A1 is hereby incorporated by reference for its jurisdictions permitting such procedures.

The XNBR and HXNBR form the preferred components of the polymer composites of the present invention, which can be characterized by standard techniques known in the art. For example, the molecular weight distribution of a polymer can be determined by Gel Permeation Chromatography (GPC) using a Waters 2690 separation Module (Waters 2690 separation Module) and a Waters 410 differential refractometer running Waters Millennium software version 3.05.01. The samples were dissolved in Tetrahydrofuran (THF) stabilized with 0.025% BHT (butylhydroxytoluene). The columns used for the determination were three consecutive columns of mixed-B gel from Polymer labs. And the reference standard used was a polystyrene standard from American Polymer standards corp.

The polymer compound of the present invention further comprises at least a halogenated butyl rubber. The term "halogenated butyl rubber" as used herein relates to a chlorinated and/or brominated butyl elastomer. Brominated butyl elastomers are preferred, and the invention is illustrated by way of example with reference to such bromobutyl elastomers. However, it should be understood that the present invention extends to the use of chlorinated butyl elastomers.

Thus, halogenated elastomers suitable for use in the practice of this invention include, but are not limited to, brominated butyl elastomers. Such elastomers may be obtained by butyl rubber (which is isobutylene and one usually C)₄To C₆A copolymer of a conjugated diene, preferably isoprene, comonomer). However, comonomers other than conjugated dienes may be used, and mention is made of vinyl aromatic comonomers substituted by alkyl groups, such as C₁To C₄Alkyl-substituted styrenes of (1). An example of such a commercially available elastomer is brominated isobutylene methylstyrene copolymer (BIMS) wherein the comonomer is p-methylstyrene.

Brominated butyl elastomers typically contain 1 to 3 wt% isoprene and 97 to 99 wt% isobutylene (based on the hydrocarbon content of the polymer) and 1 to 4 wt% bromine (based on the bromobutyl polymer). Typical bromobutyl polymers have a molecular weight expressed as the Mooney viscosity (ML 1+8 at 25 ℃) in the range of from 28 to 55.

The brominated butyl elastomer used in the present invention preferably comprises from 1 to 5 weight percent of a diene, such as isoprene, from 95 to 99 weight percent of an isoolefin, such as isobutylene (based on the hydrocarbon content of the polymer), and from 0.5 to 2.5 weight percent, preferably from 0.75 to 2.3 weight percent, of bromine (based on the brominated butyl polymer).

The stabilizer may be added to the brominated butyl elastomer. Suitable stabilizers include calcium stearate and epoxidized soybean oil, preferably used in amounts of 0.5 to 5 parts by weight per 100 parts by weight of brominated butyl rubber.

Examples of suitable Bromobutyl elastomers include Bayer * Bromobutyl 2030, Bayer * Bromobutyl 2040(BB2040), and Bayer * Bromobutyl X2, which are commercially available from Bayer Inc. Bayer * BB2040 had a Mooney viscosity of 39. + -.4 (RPML 1+8 * 125 ℃ C. according to ASTM D52-89), a bromine content of 2.0. + -. 0.3 wt.% and an approximate molecular weight Mw of 500,000 g/mol.

The composition of the polymer composite of the present invention depends on the intended use and by adjusting the amounts of nitrile rubber and halobutyl, the properties of the final composite and the resulting article can be met. Preferably, however, the polymer composite of the present invention comprises 0.01 to 20 parts by weight of at least one optionally hydrogenated carboxylated nitrile rubber polymer per hundred parts by weight halobutyl rubber, more preferably 0.1 to 5 parts by weight.

The polymer composite of the present invention further optionally comprises at least one filler. The filler may be an active or inert filler or a mixture thereof. The fillers may in particular be:

highly dispersed silicas, prepared for example by precipitation from silicate solutions or flame hydrolysis of silicon halides, having a particle size of from 5 to 1000m²A specific surface area per gram, and a primary particle size of 10 to 400 nm; the silica can optionally also be provided in the form of mixed oxides with other metal oxides, for example oxides of Al, Mg, Ca, Ba, Zn, Zr and Ti.

Synthetic silicates, such as aluminum silicate and alkaline earth metal silicates (such as magnesium silicate or calcium silicate), having 20 to 400m²A BET specific surface area in g and a primary particle diameter of 10 to 400 nm;

natural silicates, such as kaolin and other naturally occurring silicas;

glass fibers and glass fiber products (woven, extruded products) 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;

-carbon black; the carbon black used here can be prepared by the lamp black, furnace black or gas black process and preferably has a thickness of from 20 to 200m²BET specific surface area per g (DIN 66131), which is, for example, SAF, ISAF, HAF, FEF or GPF carbon black;

rubber gels, especially those based on polybutadiene, butadiene/styrene copolymers, butadiene/acrylonitrile copolymers and neoprene; or mixtures thereof.

Examples of preferred mineral fillers include silica, silicates, clays such as bentonite, gypsum, alumina, titanium dioxide, talc, mixtures thereof and the like. These mineral particles have hydroxyl groups on their surface, rendering them hydrophilic and oleophobic. This makes it difficult to obtain good interaction between the filler particles and the rubber. For many purposes, the preferred mineral is silica, especially silica prepared by carbon dioxide precipitation from sodium silicate. The dry amorphous silica particles suitably used in accordance with the present invention may have an average agglomerate particle size of from 1 to 100 μm, preferably between 10 and 50 μm, most preferably between 10 and 25 μm. Preferably, less than 10 volume percent of the agglomerate particles have a particle size of less than 5 μm or greater than 50 μm. Suitable amorphous dry silicas furthermore generally have a particle size of from 50 to 450m²BET specific surface area in terms of DIN (German industry Standard) 66131, DBP absorption in terms of DIN 53601, and a drying weight loss in terms of ISO 787/11, in a range of from 150 to 400 g of DBP per 100 g of silica, and a drying weight loss in the range of from 0 to 10% by weight. Suitable silica fillers are available under the trade names HiSil * 210, HiSil * 233 and HiSil * 243 from PPGIndustries inc. Also suitable are Vulkasil * S and Vulkasil * N supplied by Bayer AG.

Carbon black is generally advantageously used as filler. The amount of carbon black present in the polymer composite is generally from 20 to 200 parts by weight, preferably from 30 to 150 parts by weight, more preferably from 40 to 100 parts by weight. Furthermore, the combined use of carbon black and mineral fillers in the polymer composites of the invention may be advantageous. The combined ratio of mineral filler and carbon black is generally from 0.05 to 20, preferably from 0.1 to 10.

It is advantageous for the polymer composite to further comprise other natural or synthetic rubbers, for example BR (polybutadiene), ABR (butadiene/acrylic acid-C)₁-C₄-alkyl ester-copolymers), CR (polychloroprene), IR (polyisoprene), SBR (styrene/butene-copolymers) with a styrene content of 1 to 60 wt.%, NBR (butadiene/acrylonitrile-copolymers) with an acrylonitrile content of 5 to 60 wt.%, HNBR (partially or fully hydrogenated NBR-rubber) with a mooney viscosity (ML 1+4 at 100 ℃ according to ASTM test D1646) of at least 30, EPDM (ethylene/propylene/diene-copolymers), FKM (fluoropolymers or fluororubbers), and mixtures of the polymers obtained. Careful blending of conventional HNBR can often reduce the cost of the polymer composite without reducing processability. The amount of conventional HNBR and/or other natural or synthetic rubbers will depend on the processing conditions applied in the manufacture of shaped articles and can be easily obtained with few preliminary experiments.

The polymer composite further optionally includes one or more crosslinking agents or cure systems. Although the present invention is not limited to a particular curing system, 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 organic peroxides are, for example, dialkyl peroxides, ketal peroxides, aralkyl peroxides, ether peroxides, ester peroxides such as di-tert-butyl peroxide, di- (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-di- (tert-butylperoxy) -3, 3, 5-trimethylcyclohexane, benzoyl peroxide, tert-butylcumyl peroxide and tert-butylperoxybenzoate. The amount of peroxide in the polymer compound is generally from 1 to 10phr (═ per hundred parts of rubber), preferably from 4 to 8 phr. The subsequent vulcanization is carried out at a temperature in the range from 100 to 200 ℃ and preferably in the range from 130 to 180 ℃. Peroxides may conveniently be applied in the form of polymeric binders. A suitable commercially available system is for example Polydispersion T (VC) D-40P (di-tert-butylperoxy-cumene, a polymer binder) supplied by Rhein Chemie Rheinau GmbH D. Crosslinking is also affected by radiation, such as alpha-, beta-, gamma-radiation.

The rubber composition according to the present invention may further comprise auxiliary materials for rubbers such as reaction accelerators, vulcanization acceleration aids, antioxidants, foaming agents, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, plasticizers, thickeners, foaming agents, dyes, pigments, paraffins, expanding agents, organic acids, inhibitors, metal oxides, and activators such as triethanolamine, polyethylene glycol, hexanetriol, etc., which are well known in the rubber industry. The rubber auxiliaries are used in the customary amounts, which depend inter alia on the desired use. Conventional amounts are, for example, from 0.1 to 50% by weight, based on the rubber. Preferably the composition comprises from 0.1 to 20phr of an organic fatty acid as an auxiliary material, preferably an unsaturated fatty acid having one, two or more carbon-carbon double bonds in the molecule, more preferably it comprises 10 wt% or more of a conjugated diene acid having at least one conjugated carbon-carbon double bond in the molecule. Those fatty acids preferably 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. Preferably the composition comprises 5 to 50phr of an acrylate as an auxiliary material. Suitable acrylates are known from EP-A1-0319320, in particular from paragraph 3, lines 16 to 35, also from US5208294, in particular from column 2, lines 25 to 40, and also from US4983678, in particular from column 2, lines 45 to 62. Particular reference is made to zinc acrylate, zinc diacrylate or zinc dimethacrylate, or liquid acrylates such as trimethylolpropane Trimethacrylate (TRIM), Butanediol Dimethacrylate (BDMA) and ethylene glycol dimethacrylate (EDMA). It is advantageous to use different acrylates and/or metal salts thereof in combination. It is particularly advantageous to use scorch retarders such as sterically hindered phenols (e.g. methyl-substituted aminoalkylphenols, especially 2, 6-di-tert-butyl-4-dimethylaminomethylphenol) often in combination with the use of metal acrylates.

Another aspect of the invention relates to a process for preparing said polymer composite comprising at least one optionally hydrogenated carboxylated nitrile rubber polymer and at least halogenated butyl rubber, wherein said at least one optionally hydrogenated carboxylated nitrile rubber polymer and at least halogenated butyl rubber are mixed.

The components of the final polymer composite are suitably mixed together at an elevated temperature, which may range from 25 to 200 ℃. Usually the mixing time does not exceed one hour and a mixing time of 2 to 30 minutes is usually sufficient. The mixing is suitably carried out in an internal mixer, such as a Banbury mixer, or a Hakke or Brabender miniature internal mixer. The two roll mill also provides excellent dispersion of the additives in the elastomer. The extruder also provides excellent mixing at shorter mixing times. The mixing can be carried out in two or more steps and the mixing can be carried out in different apparatuses, for example in one stage in an internal mixer and in one stage in an extruder. It should be noted, however, that undesirable precrosslinking (═ scorch) is not desired during the mixing stage. For compounding and vulcanization see also: encyclopedia of Polymer science and Engineering, Vol.4, p.66 and pages thereafter (compounding) and Vol.17, p.666 and pages thereafter (vulcanization). During the curing/vulcanization process, the desired crosslinking between the halobutyl and the XNBR/HXNBR occurs and thus increases the crosslink density of the composite.

The present invention therefore relates to a process for increasing the crosslink density of halogenated butyl rubbers by mixing said halogenated butyl rubber with at least one optionally hydrogenated carboxylated nitrile rubber polymer, optionally at least one crosslinking agent and optionally a filler, and then curing the compound.

The composite composition of the present invention results in an improved cure state of the final part relative to the comparative examples, which results in improved physical properties of the final part, which can be measured by various tensile moduli and blend hardnesses.

Furthermore, the present invention provides a shaped article comprising said polymer composite of the invention comprising at least one optionally hydrogenated carboxylated nitrile rubber polymer and at least a halogenated butyl rubber. Preferred shaped articles are tires, tire components such as inner liners, treads and sidewalls, seals, adhesives and sealing compounds, coatings, cements and tapes for coating tubes.

Examples

Examples 1 to 3

The polymer compound was mixed on a mill (6X 12 inch mill, capacity 1000) with the mill temperature set at 30 ℃. The carbon black, stearic acid and oil were then added to the same mill set at 30 c in separate mixing steps. The curing agent and Vulkacitt * DM/C were then added separately in separate mixing steps to the same open mill set at 30 ℃. The formulation is as in table 1.

Therban * XT VP KA 8889 is a HXNBR commercially available from Bayer Inc.

Bayer * Bromobutyl 2030 is a Bromobutyl synthetic rubber commercially available from Bayer inc.

Carbon Black N660 Sterling-V was purchased from Cabot fire Blacks.

Stearic acid was purchased from c.p.hall.

Sunpar * 2280 is a paraffin Oil produced by Sun Oil.

Struktol * ZP 1014 was prepared from Struktol commercially available zinc peroxide.

Vulkacit * DM/C is dibenzothiazyl-disulfide, available from Bayer AG.

TABLE 1 Complex formulations

Examples	1 (comparative example)	2	3
				Therban*XT VP KA 8889	0	4	8
Bayer*Bromobutyl2030	100	100	100
				Carbon Black N660	60	60	60
Stearic acid	1	1	1
				Sunpar*2280	7	7	7
Vulkacit*DM/C	1.3	1.3	1.3
				Curing agent
Spider Sulfur	0.5	0.5	0.5
				Struktol*ZP 1014	6	6	6

Polymer composite Properties

Table 2 shows a summary of the properties of the polymer composites of examples 1-3. Example 1 was used for comparison.

Compound Mooney viscosity: the measurement was carried out at 100 ℃ using a large rotor.

Vulcanization rheometry: ASTM D52-89 MDR2000E Rheometer (Rheometer) was run at 1 radian and 1.7 Hz.

Compound mooney scorch: the measurement was carried out at 135 ℃ using a large rotor.

Stress-strain: samples were prepared by vulcanizing large sheets at 170 ℃ for tc90+5 minutes, after which appropriate samples were stained. The test was carried out at 23 ℃.

Examples	1	2	3
				Mooney viscosity of the compound
ML 1+4 at 100 deg.C	63.7	67.5	67.8
				Decay time 80% (min)	0.09	0.11	0.11
Slope (1gM/1gs)	-0.5341	-0.5011	-0.4867
				Intercept (MU)	30.557	32.9044	32.9654
Area under curve	777.3	949.7	1002.4
Mooney scorch for composites
				t5 at 135 deg.C (min)	10.9	12.2	14.2
				MDR vulcanization characteristic 1.7 Hz; 1 degree radian; 170 ℃ C: 60 minutes
MH(dN.m)	8.78	13.52	15.92
				ML(dN.m)	2.76	3.50	3.71
ΔMH-ML(dN.m)	6.02	10.02	12.21
				ts 1(min)	1.32	1.50	1.62
ts 2(min)	1.62	1.92	2.16
				ts 10(min)	1.21	1.50	1.74
ts 25(min)	1.45	2.08	2.69
				ts 50(min)	2.11	3.40	4.50
ts 90(min)	8.45	9.62	9.69
				ts 95(min)	12.53	12.78	12.24
Δt’50-t’10(min)	0.90	1.90	2.76

Examples	1	2	3
				Stress-strain (dumbbell)
Vulcanizing time (min) at 170 DEG C	15	17	17
				Stress is 10(MPa)	0.56	1.27	1.60
Stress is 25(MPa)	0.71	1.62	2.18
				Stress is 50(MPa)	0.86	2.01	2.81
Stress is 100(MPa)	1.29	2.85	3.84
				Stress is 200(MPa)	2.92	5.21	6.09
Stress is 300(MPa)	5.09	7.92	8.60
				Ultimate tensile strength (MPa)	10.55	10.94	10.18
Ultimate elongation (%)	671	443	370
				Hardness Shore A2(Pts.)	44	63	68

Δ MH-ML represents the crosslink density. It is clear from examples 2-3 (Table 2 and FIG. 1) that the addition of a small amount of hydrogenated carboxylated nitrile rubber to the bromobutyl synthetic rubber formulation results in a significant improvement in the cure state of the compound. This results in a composite with improved stiffness and increased modulus at a set elongation.

Claims (12)

1. A polymer compound comprising at least one, optionally hydrogenated, carboxylated nitrile rubber polymer and at least halogenated butyl rubber.

2. The compound of claim 1, wherein the carboxylated nitrile rubber polymer is a hydrogenated carboxylated nitrile rubber.

3. The compound of claim 1 or 2, wherein the halogenated butyl rubber is a brominated butyl rubber.

4. A compound according to any one of claims 1 to 3, wherein the carboxylated nitrile rubber is a statistically distributed copolymer.

5. The composite of any of claims 1-4, wherein the polymer composite further comprises at least one cross-linking agent.

6. The composite of any of claims 1-5, wherein the polymer composite further comprises at least one filler.

7. A process for the preparation of a polymer composite according to any one of claims 1 to 6, wherein at least one, optionally hydrogenated, carboxylated nitrile rubber polymer, at least halogenated butyl rubber, optionally at least one filler and optionally at least one crosslinking agent are mixed.

8. A shaped article comprising at least one, optionally hydrogenated, carboxylated nitrile rubber polymer and at least halogenated butyl rubber.

9. The shaped article according to claim 8 in the form of a tire or tire component.

10. A process for increasing the crosslink density of halogenated butyl rubber by mixing halogenated butyl rubber with at least one optionally hydrogenated carboxylated nitrile rubber polymer, optionally at least one crosslinking agent and optionally a filler, and then curing the compound.

11. A process according to claim 9, wherein the carboxylated nitrile rubber is a statistically distributed copolymer.

12. A process according to claim 9 or 10, wherein the halogenated butyl rubber is a brominated butyl rubber.