BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composition suitable for use in hoses, including automotive radiator coolant hoses, air conditioning hoses and steam hoses; and hoses comprising the composition.

2. Description of Information Disclosures

Hoses made from synthetic or natural rubbers and methods for producing the hoses are known. Hoses used to conduct fluids to and from automotive radiators are described, for example, in U.S. Patent 4,096,888; U.S. Patent 4,698,890; and U.S. Patent 4,158,033, the teachings of which are hereby incorporated by reference.

Although there are many commercially available types of automotive radiator hoses, there is still a need to improve the properties of these hoses, such as resistance to water or coolant diffusion, heat resistance and compression set.

Rubber based steam hoses are also well known in the art. One problem with such hoses is that

moisture often permeates the rubber portion of the hose. When the moisture is cooled and then reheated, the trapped moisture can cause the formation of blisters or partial blowouts. This effect is known as "popcorning".

Because of its good impermeabilities, halogenated butyl rubber has been used for steam hoses in an effort to reduce this popcorning effect. There exists, however, a continuing need for hose compositions with improved impermeability and heat reistance.

It has now been found that hoses that are made from a composition comprising certain halogen- containing copolymers of a C4 to C7 isomonoolefin and a para-alkylstyrene containing a critical amount of the para-alkylstyrene moiety and a critical amount of chemically bound halogen have improved properties.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a hose composition comprising: (1) a halogen- containing copolymer of a C4 to C ₇ isomonoolefin and a para-alkylstyrene, said copolymer comprising at least about 5 weight percent of said para-alkylstyrene, and at least about 0.4 mole percent of said halogen; (2) a component selected from the group consisting of a filler, a rubber compounding additive and mixtures thereof; and (3) a curing agent.

In accordance with the invention, there is also provided a vulcanized elastomeric hose comprising an inner tube, a reinforcing member and an outer

cover, wherein at least a portion of said hose comprises a composition comprising: (1) a halogen- containing copolymer of a C4 to C7 isomonoolefin and a para-alkylstyrene, said copolymer comprising at least about 5 weight percent of said para-alkylstyrene, and at least about 0.4 mole percent of said halogen; and (2) a component selected from the group consisting of a filler, a rubber compounding additive and mixtures thereof. For steam hose applications the copolymer should preferably contain at least about 0.5 mole percent of said halogen.

DETAILED DESCRIPTION OF THE INVENTION

The hose composition of the present invention comprises a halogen-containing copolymer of a C4 to C7 isomonoolefin and a para-alkylstyrene, fillers, rubber compounding additives and a curing agent with or without curing agent accelerators.

Suitable halogen-containing copolymers of a C4 to C7 isomonoolefin and a para-alkylstyrene for use as a component of the present hose composition comprise at least 5 weight percent of the para- alkylstyrene moiety. The para-alkylstyrene moiety may range from about 5 weight percent to about 20 weight percent of the copolymer. Furthermore, the suitable copolymers comprise at least about 0.4 mole percent, preferably at least about 0.5 mole percent of the halogen. The halogen content of the copolymer may range from about 0.4 to about 1.0 mole percent. The halogen may be bromine, chlorine, and mixtures thereof. Preferably, the halogen is bromine. The major portion of the halogen is chemically bound to

the para-alkyl group, that is, the halogen-containing copolymer comprises para-halo alkyl groups.

The copolymers of the isomonoolefin and para-alkylstyrene useful to prepare the halogen- containing copolymers suitable as component of the hose composition of the present invention include copolymers of isomonoolefin having from 4 to 7 carbon atoms and a para-alkylstyrene, such as those described in European patent application 89305395.9 filed May 26, 1989, (Publication No. 0344021 published November 29, 1989) . The preferred isomonoolefin comprises isobutylene. The preferred para-alkylstyrene comprises para- ethylstyrene. Suitable copolymers of an isomonoolefin and a para-alkylstyrene include copolymers having a number average molecular weight (Mn) of at least about 25,000, preferably at least about 30,000, more preferably at least about 100,000. The copolymers also, preferably, have a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) , i.e., Mw/Mn of less than about 6, preferably less than about 4, more preferably less than about 2.5, most preferably less than about 2. The brominated copolymer of the isoolefin and para-alkylstyrene by the polymerization of these particular monomers under certain specific polymerization conditions now permit one to produce copolymers which comprise the direct reaction product (that is, in their as-polymerized form) , and which have unexpectedly homogeneous uniform compositional distributions. Thus, by utilizing the polymerization and bro ination procedures set forth herein, the copolymers suitable for the practice of the present invention can be produced. These copolymers, as determined by gel permeation chromatography (GPC) demonstrate narrow molecular weight distributions and

substantially homogeneous compositional distributions, or compositional uniformity over the entire range Of compositions thereof. At least about 95 weight percent of the copolymer product has a para-alkylstyrene content within about 10 wt. percent, and preferably within about 7 wt. percent, of the average para- alkylstyrene content for the overall composition, and preferably at least about 97 wt. percent of the copolymer product has a para-alkylstyrene content within about 10 wt. percent and preferably within about 7 wt. percent, of the average para-alkylstyrene content for the overall composition. This substantially homogeneous compositional uniformity thus particularly relates to the intercompositional distribution. That is, with the specified copolymers, as between any selected molecular weight fraction the percentage of para-alkylstyrene therein, or the ratio of para-alkylstyrene to isoolefin, will be substantially the same, in the manner set forth above.

In addition, since the relative reactivity of para-alkylstyrene with isoolefin such as isobutylene is close to one, the intercompositional distribution of these copolymers will also be substantially homogeneous. That is, these copolymers are essentially random copolymers, and in any particular polymer chain the para-alkylstyrene and isoolefin units will be essentially randomly distributed throughout that chain.

The halogen-containing copolymers useful in the practice of the present invention have a substantially homogeneous compositional distribution and include the para-alkylstyrene moiety represented by the formula:

in which R and R ¹ are independently selected from the group consisting of hydrogen, alkyl preferably having from 1 to 5 carbon atoms, primary alkyl halides, secondary alkyl halides preferably having from 1 to 5 carbon atoms, and mixtures thereof and X is selected from the group consisting of bromine, chlorine and mixtures thereof, such as those disclosed in European patent application 8930595.9 filed May 26, 1989, (Publication No. 0344021 published November 29, 1989).

Various methods (which are known and now in the public domain) may be used to produce the copolymers of isomonoolefin and para-alkylstyrene, as described in said European publication.

One of the advantages of a isobutylene/para- methylstyrene copolymer incorporating phenyl rings (and no backbone unsaturation) is that greatly enhanced ozone resistance is achieved.

The hose composition of the present invention also comprises a component selected from the group consisting of a filler, a rubber compounding additive and mixtures thereof.

The filler may be a non-reinforcing filler, a reinforcing filler, an organic filler, and an inorganic filler, and mixtures thereof.

Suitable fillers include calcium carbonate, clay, silica, talc, carbon black and mixtures thereof.

Suitable rubber compounding additives include antioxidants, stabilizers, rubber processing oils, pigments and mixtures thereof. The rubber process oils may be paraffinic or naphthenic process oils. Suitable antioxidants include hindered phenols, amino phenols, hydroquinones, alkyldiamines, a ine condensation products and the like. The preferred additives are fatty acids, low molecular weight polyethylene, waxes, and mixtures thereof. A preferred fatty acid is stearic acid. Mixtures of other fatty acids can be used with the stearic acid.

The hose composition also comprises a curing agent. Any known curative system suitable for vulcanization of rubber may be used.

Suitable curing agents include peroxide cures, sulfur cures and non-sulfur cures. For example, the curing agent may be zinc oxide, optionally, curing agent accelerators may be used such as dithiocarbamates, thiurams, thioureas, and mixtures thereof, zinc oxide-free cures may also be used such as, for example, litharge; 2-mercaptoimidazoline; diphenyl guanidine; 2-mercaptobenzimidazole; and N,N\'- phenylene-bismaleimide.

Resin curatives may also be used as curative component of the hose composition, such as, phenolic

resins, brominated phenolic resins, urethane resin, etc. organic peroxides may be used as curing agents, such as, for example, dicumyl peroxide, benzoyl peroxide, α, α\'-Bis(tertiary butyl peroxy) diisopropyl benzene, and the like.

The hose composition of the present invention may comprise the specified halogen- containing copolymer of a C4 to C7 isomonoolefin and a para-alkylstyrene in an amount ranging from about 35 to 65, preferably from about 45 to about 55 weight percent, the total amount of fillers and additives in an amount ranging from about 35 to 65, preferably from about 45 to 55 weight percent, and the curing agent in an amount ranging from about 0.5 to 5.0, preferably from about 1.5 to 3.0 weight percent, all said percentages being based on the weight of the total hose composition.

The hose composition may be vulcanized by subjecting it to heat and/or light or radiation according to any conventional vulcanization process. Typically, the vulcanization is conducted at a temperature ranging from about 130°C to about 250*C, preferably from about 150°C to about 200 ^β C, for a time period ranging from about 1 to about 150 minutes.

The hose composition of the present invention may be used in the production of any type of hoses, for example, automotive radiator coolant hose, air conditioning hose, steam hose and the like.

Automotive radiator coolant hoses typically comprise an inner tube and an outer cover and a yarn or fiber reinforcement layer between the tube and cover. Steam hoses and some other types of hoses also

use reinforcements and/or other layers between the inner tube and the outer cover. In accordance with the present invention, the hose composition is used to fabricate at least a portion of the hose.

Thus, the hose composition of the present invention may be used to produce the inner tube and/or the outer cover of the hose. Preferably, the hose composition is used to produce at least a portion of the inner tube.

The hose may be produced by any conventional method. For example, the unvulcanized hose composition may be formed into an elongated tube. The tube and reinforcement is then positioned on a mandrel. A cover material may be applied to the outer surface of the tube. Pressure may be applied either directly or by wrapping the hose in a tape fabric, such as a plastic tape, and, thereafter, subjecting the hose to heat and steam pressure to vulcanize the hose.

A typical hose generally comprises an inner tube, an outer cover and a reinforcement. The inner tube is adapted to contain the fluid or vapor to be conveyed by the hose and to resist the internal pressure of the material being conveyed or the external forces acting on the hose. The cover protects the hose from mechanical and environmental damage.

A preferred method of manufacturing hoses, such as automotive hoses, is the extrusion process.

For example, to produce a hose utilizing the hose composition of the present invention by the extrusion process, the hose composition is heated in an extruder

suitable for extruding rubber. The extruder acts like a pump, thereby forcing the softened rubber mass through a pin and ring die configuration which causes the composition to take the shape of a tube. The tube is cooled immediately in a water trough. Subsequently, the reinforcement is applied either by spiralling, knitting, or braiding a textile yarn around the tube. Thereafter, the reinforced tube is covered with the hose composition of the present invention or with a different composition, such as compositions conventionally used in outer tube covers, depending on the desired end usage of the hose, by passing the reinforced tube through a cross-head extruder. The resulting extruded, covered and reinforced tube is cooled again in a water trough, then cut into hose pieces of desired lengths which are placed on preformed mandrels. Thereafter, the hose pieces are vulcanized in a steam autoclave.

For steam hose applications, one or more layers of brass-coated steel wire may be used as a reinforcement.

The following examples are presented to illustrate the invention.

Examples

Experiments were conducted to compare the cure response and physical properties of formulations comprising brominated isobutylene-para-methylstyrene copolymer of the present invention to a formulation comprising a bromobutyl rubber. The brominated isobutylene-para-methylstyrene copolymer used in these

formulations contained the bromine in the para-methyl- styrene moiety. The master batch formulations to which the brominated isobutylene-paramethylstyrene copolymers were added was the same as the master batch formulation to which the bromobutyl rubber was added. Different curing agents were used in Formulations A through E than in Formulation F, as shown in Table I. The curing agents in Formulations A through E comprised zinc oxide and dipentamethylene thiuram hexasulfide. The curing agents in Formulation F comprised zinc oxide, benzothiazyl disulfide and tetramethylthiuram disulfide. The formulations in accordance with the present invention were designated A through E. The comparative formulation containing bromobutyl rubber was designated F. The bromobutyl rubber used in Formulation F comprised 2 wt. percent bromine and had a Mooney Viscosity of 37 (ML 1 + 8) at 125"C (i.e., Exxon Bromobutyl Grade 2233, Exxon Chemical Company) .

The bromobutyl rubber used in Formulation F is designated "Copolymer T" in Table I. The bromoisobutylene para-methylstyrene copolymers used in Formulations A through E are designated copolymers Z, Y, X, w and M in Table I. These latter copolymers had different bromine contents and other properties as listed in Table I. All the compounds were cured for 20 minutes at 160°C in a steam heated compression mold.

The formulations and the results of these tests are shown in Table I.

The Mooney Viscosities in Table I were all measured in accordance with ASTM D1646.

TABLE 1

Formulation B D

Copolymer T 100.0 Copolymer Z 100.0 Copolymer Y 100.0 Copolymer X 100.0 Copolymer W 100.0 Copolymer M Carbon Black (1) Carbon Black (2) Clay (3)

Hydrocarbon oil (4) Fatty acid mixture Polyethylene (5) Stearic Acid Zinc oxide MBTS (6) TMTDS (7) DPTHS (8) 1.0 1.0 1.0 1.0 1.0

Copolymer Mooney

Viscosity, 125°C 59 31 28.5 28.5 29 37 Para-methylstyrene, wt.% 5.0 10.0 10.5 5.0 5.0 Bromine, πιol.% 0.5 0.8 1.2 0.6 1.4 2.0

Mooney Scorch (MS) (9) 132°C Minutes to 10 Point Rise 10.0 8.7 8.0 9.9 6.5 6.9 Mooney Viscosity (ML) 100°C 1 + 8 Minute Reading 53.9 36.6 35.1 35.6 3 44.9

TABLE 1 (Continued)

TABLE 1 Continued

Formulation

Cure Hardness Change, Pts. 8

20/160 Tensile Retained, % 14

Elongation Retained, % 33

Aged Hardness, Shore A (14) 46

336 100% Modulus, MPa 1.00

Hrs. 200% Modulus, MPa 2.12 at Tensile Strength, MPa 10.03

103°C Elongation, % 646

IN 50% COOLANT/H ₂ 0, V/V (15)

Cure Hardness Change, Pts. -3 -5 -3 -5 -5 ^• 11

20/160 Tensile Retained, % 102 102 98 104 86 97

Elongation Retained, % 91 92 86 94 85 83

Weight Change, % 3.46 4.02 4.48 3.58 5.01 4.96

Volume Change, % 2.73 3.38 3.86 3.18 4.74 4.46

Compression Set, Plied, (16) 70 Hrs. at 150°C 47.84 70.82 87.17 58.37 91.79 90.75

Compression Set, %

70 Hrs. at 70°C + 3 Hrs. at 23°C 34.52 45.38 55.60 41.22 63.31 76.80

TABLE 1 (Continued)

(1) Carbon black ASTM N326.

(2) Carbon black ASTM N770.

(3) Siloxane-treated clay.

(4) Hydrocarbon oil ASTM type 104B.

(5) Polyethylene, low molecular weight.

(6) MBTS means benzothiazyl disulfide.

(7) TMTDS means tetramethylthiuram disulfide.

(8) DPTHS means dipentamethylene thiuram hexasulfide.

(9) ASTM D 1646.

(10) ASTM D 2084.

(11) ASTM D 412.

(12) ASTM D 624.

(13) ASTM D 573.

(14) ASTM D 471.

(15) Coolant is a commercially available antifreeze mixture, predominantly ethylene glycol, 50% volume of antifreeze per 50% volume of water.

(16) ASTM D 395.

As can be seen from the data of Table I,

Formulations A, B, C, D, and E, which were formulations in accordance with the present invention, had a better cure activity than comparative formulation F.

Furthermore, the state of cure as determined by the difference between the maximum torque (MH) and the minimum torque (ML) on the curemeter plot was higher for Formulations A through E. Stress strain properties, including modulus, tensile strength and elongation also indicated that Formulations A through E had an improved state of cure. This is additionally indicated by the compression set results which were generally lower for Formulations A through E of the present invention compared to that of comparative Formulation F. This characteristic is important for maintaining sealability in hoses for conducting fluids. The formulations of the present invention also had significantly better retention of physical properties after being aged in hot air for one week at temperatures of 150 ^β C to 165 ^β C, respectively.

A second series of experiments were conducted to compare the cure responses and physical properties of formulation comprising brominated isobutylene-paramethylstyrene copolymer of the present invention to a formulation comprising a bromobutyl copolymer typically used in steam hose applications. As with the prior series of experiments the brominated isobutylene-para-methylstyrene copolymer used in the formulations below contained the bromine in the para- methyl styrene moiety. The master batch formulations to which the brominated isobutylene-para-methylstyrene copolymers were added was the same as the master batch formulation to which the bromobutyl rubber was added.

Different curing agents were used in Formulations G through J than in Formulation K. The curing agents in Formulations G through J were the same as for Formulations A through E and the agents for Formulation K were the same as for Formulation F. The Formulations in accordance with the present invention are designated G through J. The comparative formulation containing bromobutyl rubber was designated K. The bromobutyl used in Formulation K comprised 2.0 weight percent bromine and had a Mooney viscosity of 51.4 (ML 1+8) at 100 ^β C (ie., Exxon Bromobutyl Grade 2244, Exxon Chemical Company).

The bromobutyl rubber used in Formulation K is designated "Copolymer AA" in Table II. The bromoisobutylene para-methylstyrene copolymer used in Formulations G through J are designated copolymers AB, AC, AD and AE in Table II. These latter copolymers had different bromine contents and other properties as listed in Table II. All the compounds were cured for 20 minutes at 160"C in a steam heated compression mold.

The formulations and results of these tests are shown in Table II.

The Mooney viscosities in Table II were all measured in accordance with ASTM D1646.

FORMULATTONS H K

Copolymer AB 100.0 Copolymer AC 100.0 Copolymer AD 100.0 Copolymer AE 100.0 Copolymer AA Carbon Black (1) Plasticizer (2) Stearic Acid An ioxidant DPTHS (Tetrone A) TMTDS MBTS

Formula Weight 159.5 159.5 159.5 159.5 165.0

Mooney Scorch(MS) 132 C Minutes to 3 Point Rise 8.6 8.8 6.2 4.9 7.5

Mooney Viscosiry (ML) 100 C 1+8 Minuτe Reading 52.0 41.0 38.2 34.2 51.4

Rheometer 160 C ML

30 Min. otor, I.7HZ MH

3 Degree Arc TS2

50 Full Scale 1,2,4 T ^, 90

100 Full Scale 3,5-8 MH-ML

Original Physical Properties Press Cure 20 Minutes at 160\'

Hardness, Shore A 46 46 \' 54 100% Modulus, MPa 0.83 0.83 1.38 300% Modulus, MPa 3.71 3.60 6.62 Tensile Strength, MPa 15.68 13.62 12.81 Elongation, % 805 782 540

* Data based on Resin Cured Exxon Butyl 268 in the same compound formulation. ** Bromobutyl compound aged 70 hours at 150 C.

(1) Carbon Black ASTM N330

(2) Sunpar 2280, Paraffinic oil, ASTM D2226 Type 104B

Table III shows the results of a comparison of a brominated isobutylene para-methylstyrene copolymer with Chlorobutyl in typical steam hose compositions. The data shows that compounds based on the brominated isobutylene para-methylstyrene copolymer have better scorch safety (high TS2) , faster cure (lower T90) , significantly lower compression set and significantly better retention of hardness, tensile strength and elongation after aging in steam and hot air.

The brominated isobutylene para-methyl styrene copolymer (Designated copolymer AF) contained 5 wt % paramethylstyrene and 0.7 mole % bromine. The chlorobutyl rubber, copolymer AG contained about 1.1 weight % chlorine.

TABLE III - STEAM HOSES

STEAM HOSES BASED ON BR-XP-50

TABLE III (Continued,-

(22 hRS./70 ^* C)

43 16.5 Not Available 15

(1) Carbon black, ASTM N550

(2) Carbon black, ASTM N330 (3) Carbon black, ASTM N339

(4) Naphthenic petroleum oil, ASTM type 104A

(5) Paraffinic rubber frozen oil, ASTM type 104B

(6) Paraffinic rubber frozen oil, ASTM type 104B

(7) 2.2\'-methylene-bis(4-methyl-6-t-butylphenol) (8) Aliphatic hydrocarbon tackifying resin, manufactured by Exxon Chemical Co.

(9) Alkyl phenol-formaldehyde resin

The Mooney viscosities in Table II were all measured in accordance with ASTM D1646.