GB2223019A

GB2223019A - Adhesive compositions

Info

Publication number: GB2223019A
Application number: GB8916672A
Authority: GB
Inventors: Cheng Teik Loo
Original assignee: MALAYSIA RUBBER RES INST
Current assignee: MALAYSIA RUBBER RES INST
Priority date: 1988-07-21
Filing date: 1989-07-21
Publication date: 1990-03-28
Anticipated expiration: 2009-07-21
Also published as: MY106610A; GB8817391D0; GB8916672D0; DE3924002A1; GB2223019B; JPH02110182A

Description

0 ADHESIVE COMPOSITIONS This invention relates to novel adhesive

compositions derived from epoxidised cis-1,4 POlyi3oprene. in particular, it relates to the adhesive compositions based on epoxidised natural rubber (ENR) for bonding rubbers to a variety of substrates including metals and rubbers.

The use of adhesive compositions for bonding rubbers to various metals is well known. Generally, an important requirement of such an adhesive is that it should not gel and it should retain its adhesion ability on standing for long periods of time. The adhesive should bond rubbers readily to metals upon heating of the assembly under pressure. To give the versatility in its application, the same adhesive is often required to bond a range of commonly used elastomers to metals. Examples of co nly used elastomers in rubber to metal assemblies include natural rubber (NR), styrene butadiene rubber (SBR), butadiene acrylonitrile rubber (NBR) and polychloroprene rubber (CR). In addition, the same adhesive is sometimes required to bond vulcanised rubbers to metals and to themselves. In practice, rubber to metal adhesives are courwrcially available as single coat systems and as two coat systems. When resistance to environmental conditions is required, a two cost system consisting of a primer coat applied over the metal substrate and a cover coat interspersed between the rubber and the primer is always employed.

It is the principal objective of this invention to provide novel adhesive compositions based on epoxidised natural rubber for use as cover adhesives to bond avariety of vulcanisable and vulcanised rubbers to metals and to themselves.

1 Another objective is to provide novel adhesive compositions based on epoxidised natural rubber for use as a general purpose primer adhesive.

Still another objective is to provide novel adhesive compositions based on epoxidised natural rubber for use as single coat adhesives for bonding chlorinated polymers to metals and to themselves.

A further objective is to provide novel adhesive compositions which are shelf stable and which markedly retain their adhesion ability even after prolonged storage and atmospheric exposure.

Detailed Description of the Invention

Epoxidised natural rubber (ENR) is prepared by the partial epoxidation of natural rubber latex with a peracid. Essentially, ENR of any desired level of epoxidation from 1 to 90 mole % can be prepared. These polymers and their preparations are disclosed in U.K. Patent 2113692A.

The first set of novel adhesive compositions based on ENR is suitable for use as cover adhesives to bond a variety of vulcanisable and vulcanised polar polymeric materials to primed metals and to themselves. The adhesive compositions comprise at least one grade of ENR, a filler and optionally a cure system. The level of the epoxidation in the epoxidised natural rubber used in the present invention will range from 1 to 90 mole %. Preferably, however, the epoxide content of the ENR will not be less than 25 mole % since epoxide contents of less than 25 mole % tend to give low bond strengths. The International Specification level for peel adhesion values between rubber bonded to rubber and rubber bonded to metal is at least 7N/mm. We have found that the use of ENR having an epoxide content of

4 mole '16 and above in the present invention makes it possible to achieve similar or even greater peel adhesion values. Therefore, most preferably, the ENR used in the present invention will have an epoxide content of at least 50 mole %. The types of filler suitable for these adhesive compositions are carbon black and/or hydrated silica present in an amount varying from 0 to 100, preferably 10 to 50, parts by weight per 100 parts of ENR. The cure system may be any of the typical sulphur or non-sulphur cure systems as used in the vulcanisation of diene rubbers such as ENR, natural rubber and the like. The cure system for ENR is optional because while it improves the strength property of ENR, its omission in the adhesive composition does not materially affect the adhesion strength. Other additives such as cure retarder, antioxidant, pigment, extender and dispersing agent can be incorporated into the adhesive compositions of this invention.

Polar polymeric materials which can be bonded using these cover adhesives of this invention include chlorinated polymers such as CR, chlorosulphonated polyethylene (Hypalon), polyvinyl chloride (PVC), chlorinated natural rubber and the like; and polar rubbers such as NBR, polyurethane, ENR and the like.

The ENR cover adhesives of this invention can be used in combination with any commercial primer adhesive commonly available. Examples of commercial primers are Chemlok 205 of Lord Corporation, Cilbond 10 and Cilbond 17 of Compounding Ingredients Ltd and Megum 3270 of Metallgesellscraft. The ENR cover adhesives of this invention can also be used in combination with the ENR primer adhesives presented hereinafter in this patent application.

The adhesive compositions of this invention may be applied as a dry layer film or as a solution. There are many solvents which can be used to prepare the solution of desired solid content. Suitable solvents include benzene, toluene, xylene, trichloroethylene methyl, ethyl ketone and the like. Depending on the required viscosity of the adhesive composition for various modes of application such as spraying, brushing and dipping, the total solid content in the solution adhesive can vary between 5% and 50%. The preferred solid conten,t is between 15% and 40%. Any solvent employed should be readily volatile so that a lengthy drying period is not encountered.

Bonding, using the adhesive compositions, can take place at elevated temperatures. Preferably, however, the temperature for affecting the adhesion using the adhesive compositions of this patent ranges from 140 0 c to 170 0 C. Typically, the time required for bonding to occur ranges from 5 to 60 minutes.

A particular advantageous feature of this invention is that the herein described adhesive compositions are time stable. After 5 months of storage at 280C, no sign of gelling is observed and the adhesives still provide the same adhesion as that of the freshly prepared adhesives. Since none of the components in the adhesive compositions is water sensitive, the bondability of the adhesive compositions of this invention is not affected by traces of water in solvents or by exposure to the atmosphere.

An important aspect of this invention resides in the excellent layover characteristics of the adhesive-coated metal substrate. The adhesivecoated metal substrate remains effective and tack-free after evaporation of solvent. After storing for a month or longer, the adhesive-coated metal still provided excellent adhesion to vulcanisable or vulcanised polar polymeric materials.

The second set of adhesive compositions of this invention is suitable for use as general purpose primer adhesives for metals. Depending on the adhesive compositions, they are also suitable for use as single coat adhesives for bonding polar polymeric materials, especially chlorinated polymers, to metals and to themselves.

The second set of adhesive compositions of this invention comprises an adhesive composition derived from the first set of adhesive compositions described earlier in combination with at least one of a carboxylic acid, a chlorinated polymer and a phenolic resin.

The invention of the-second set of adhesive compositions as primers and single coat systems is based on the discovery that when ENR, particularly ENR with a high epoxidation level, is heated in the presence of a carboxylic acid, the resulting rubber shows enhanced adhesion to metals. Similar behaviour is observed when a chlorinated polymer or a phenolic resin is used instead of carboxylic acid. It is believed that during heating, the carboxylic acid, the chlorinated polymer and the phenolic resin can each cause the ring opening of epoxide groups in ENR with the resulting formation of. rubber-bound polar groups including under this invention substituted aliphatic Generally, (Ka) in the range of preferred. lower than 1 hydroxy groups which enhance adhesion to metals.

The carboxylic acids suitable include unsubstituted and and aromatic carboxylic acids.

carboxylic acids having an acidity constant 1.5 x 10-5 to 1.0 x 10-3 are Carboxylic acids having acidity constants x 10- 5 do not give significant advantages. Carboxylic acids having acidity constants greater than '1.0 x 10-3 have a greater tendency to cause gelling of the adhesive on storage. Suitable examples are benzoic acid and chloro-, bromo-, methoxy- and hydroxy-substituted benzoic acids. The amount of the carboxylic acid present for the adhesives j i 7 1 1 in the various samples of adhesives tested ranges from I to 30 parts by weight per 100 parts of ENR. The preferred carboxylic acid is benzoic acid in amounts ranging from 5 to 20 parts. Chlorinated polymers include chlorinated natural rubber, polychloroprene, chlorinated polyvinyl chloride and the like. A suitable example is chlorinated natural rubber (Alloprene from Imperial Chemical Industries). Phenolic resins include terpene-modified and heat-reactive types. A suitable example of phenolic resin is SP154 resin from Schenectady. Both chlorinated natural rubber (Alloprene) and phenolic resin (SP154) are used in the herein described adhesive compositions in amounts ranging from I to 300. However best results are obtained when 10 to 150 parts by weight per 100 parts of ENR are used.

The ENR primer adhesives and the ENR single coat adhesives of this invention can be used to bond metallic substrates such as iron, steel, lead, aluminium, copper, brass, bronze, Monel metal, nickel, zinc and the like.

As a general purpose primer coat, the ENR adhesive compositions of this invention can be applied on a wide variety of metallic substrates. The primed metals can be coated with any commercial cover adhesive such as Cbemlok 220, Cilbond 58 or ENR cover adhesives described earlier in this patent. Such coated metals can be bonded to a wide variety of vulcanisable rubbers. The adhesion provided by the ENR primer adhesives is beat stable and resistant to boiling water.

As a single coat adhesive, the adhesive compositions provide excellent adhesion between unprimed metals and chlorinated polymers such as polychloroprene, chlorosulphonated polyethylene, 1 k polyvinyl chloride and the like. In addition, the same adhesive compositions can also be employed as cover adhesive to bond the chlorinated polymers and polar rubbers such as NBR, polyurethane, ENR and the like. As a cover adhesive, the adhesive compositions of this invention exhibit excellent resistance to environmental conditions. Good adhesion of the rubber to metal assembly is retained after subjecting the assembly to treatments of 'boiling water, diluted acid and alkali, heated ASTM No. 3 oil, or aerated salt solution.

Depending on the adhesive compositions, particularly on the type and dosage of the carboxylic acid, the bonding can take place at room temperature or at elevated temperature. Also, depending on the adhesive compositions, the hereindescribed compositions can be made time stable. Further, the adhesives are not water sensitive and thus the bondability of the adhesives of this invention is not affected by traces of water in solvents used or by exposure to the atmosphere.

The first and second sets of adhesive compositions described earlier in this patent have inadequate bondability with non-polar rubbers such as natural rubber (NR), styrene butadiene rubber (SBR) and polybutadiene (PB). Since NR and SBR are commonly used in rubber to metal bonded products, it is highly desirable to improve the bondability of ENR adhesives with these non-polar rubbers.

It is known in the prior art that the adhesive compositions containing a surfeit of sulphur can bond a wide variety of rubbers including non-polar rubbers to metals. It is however not known how the presence of a high amount of sulphur affects the bondability of the ENR adhesive compositions deberibed herein with respect to rubber to metal bonding.

The third set of adhesive compositions of this invention comprise an adhesive composition derived from 9 - either the first or the second set of the adhesive compositions described earlier in this patent in combination with 10 to 60% by weight of sulphur, based on the total solid content of the adhesive composition. The preferred percentage of sulphur is between 25% and 50%.

In accordance with the present invention, the above described adhesive compositions are capable of bonding both the non-polar and polar rubbers such as NR, SBR, PB, CR, NBR and the like to primed or unprimed metals and to themselves.

Depending on the adhesive compositions, particularly on the type and dosage of the carboxylic acid, the bonding can take place at room temperature or at elevated temperature. Also, depending on the adhesive compositions, the hereindescribed compositions can be made time stable.

The invention is further described by the following specific examples which are given for the purpose of illustration only and are not intended to limit the scope of this invention in any way.

The peel adhesions are tested according to BS 903: Part 21, Method B. Unless stated otherwise, all adhesion tests are carried out at 23 0 C.All the metal plates are grit-blasted before applying the adhesive coat. The adhesion failure is expressed in terms of percentage of failure in the rubber body. In the data given in the examples, the amounts of ingredients are given in parts by weight. The mix formulations of various rubber stocks used in the peel adhesion tests are as shown in Table 1.

16 Table 3: Formulations of the rubber stocks Rubber stock NR SBR PB NBR ENR-25 NR (SMR L) SBR ( 1502) PB (CB 11) NBR (Krynac 803) ENR (25 mole Z) S RE Aromatic oil Zinc oxide Stearic acid Antioxidant MDR Sulphur 2 2 2 2 2 1.2 1.2 40 5 5 2 2 2 1.2 1.2 1.2 5 5 2 2 2 40 5 5 2 2 2 Polychloroprene 100 Millable Polyurethane 100 (Bayren 211) (Adiprene CM) SRF 40 HAF 40 Aromatic oil Cumarone Inden Resin is Antioxidant 2 Zinc stearate 1 Magnesium oxide 4 MBTS 4 Zinc oxide 5 "T 1 Na-22F 0.6 WC 0.4 ZBuD 0.4 Sulphur 2 Chlorosulphonated Polyethylene 100 Polyvinyl chloride 100 (Hypalon 40) SRF 40 Dioctyl phthalate 25 Aromatic oil 5 Natural rubber 25 Magnesium oxide 10 HVA-2 I Lead oxide 10 Tetrone A 0.75 IIBT 0.75 11 EXAMPLE 1

Dry adhesive compositions A,B,C and D are first prepared on a laboratory two-roll mill and then dissolved in equal proportion of toluene and methyl ethyl ketone to achieve 20% total solid content. The ENR which has been subjected to appropriate extent of mastication is flly soluble in the stated solvents whereas the other ingredients in the adhesive compositions are either dissolved or dispersed in the rubber solution.

Adhesive (Parts by weight) A. B C D.

ENR (50 mole %Epoxide) Carbon black (HAF) Hydrated silica Zinc oxide Stearic acid,V R Sulphur 100)00 100 100 20 20 1 1.5 1 The ENR adhesive A,B,C and D are each used as a cover adhesive in combination with primer Chemlok 205.to bond compounds of polychloroprene, hypalon, NBR, millable polyurethane and ENR (25 mole % epoxide) to cold- rolled steel. The rubber to steel test pieces are prepared by compression at 1600C for 20 minutes. Peel adhesion tests give the following results:

12.

ENR Adhesive Rubber Compound Peel Adhesion Rubber Failure (NI=) (%) A CR 9 so A Hypalon is 100 A PVC 11 20 B CR Is 100 B Hypalon 16 100 B PVC is 30 B NBR 9 60 B Polyurethane 12 100 B ENR 11 100 (25 mole 2 Epoxide) c CR is 100 c Hypalon 16 100 c NBR 8.5 40 D CR 14 100 D Hypalon 18 100 D NBR 8 so D Polyurethane 20 100 D ENR 11 100 (25 mole % Epoxide) 1 b k As can be seen from the data, Adhesives A,5,C and D give excellent adhesion with the chlorinated and polar rubber compounds. In most cases, the rubber cannot be stripped from the metal without tearing into the body of the rubber.

ELE 2 Steel plates are first coated with each of three commercial primers, Chemlok 205, Cilbond 10 and Cilbond 17 and then coated with cover Adhesive B. The Polychloroprene compound is bonded onto such coated platesat 160 0 C for 20 minutes. Peel adhesion tests give the following results:

Primer Peel Strength Rubber Failure (NImm) (%) Chemlok 205 Is 100 Cilbond 10 13 100 Cilbond 17 12.5 100 The data presented here illustrate the versatility of cover Adhesive B in combination with commercial primer adhesives.

EMPLE 3 Polychloroprene to steel test pieces are prepared as described in example 1 using Chemlok 205 in combination with cover Adhesive C. They are then exposed to various environmental 14 1 conditions as summarised in Table 2. To ensure effective exposure, the rubber body of the test piece is bent back from the steel substrate. Peel adhesion of the test pieces are carried out before and after the environmental exposure. Data in Table 2 illustrate that the Adhesive C has good resistance to environmental conditions.

Table 2: Environmental tests on cover Adhesive C Conditions Peel Strength Rubber Failure (Nlmm) (%) None is 100 Water at 28 0 C, 7 days 17 100 Boiling water, 2 hours 16 100 5% EC1 at 28 0 C, 7 days 17 100 5% NaOH at 280C, 7 days 18 100 5% NaCl, aerated at 280C, 7 days 18 100 ASTM No 3 oil at 1000C, 5 days 5 100 EXA12.ME 4 Steel plates are primed with Chemlok 205 and then coated with cover Adhesive C. The polychloroprene compound is bonded onto such coated plate- - at 1600C for 20 minutes. Peel adhesion tested at different temperatures give the following results:

p Is Tes tin g 0 Temperature Peel Adhesion Rubber Failure ( C) (N /m) (%) 23 is 100 so 9 100 3.5 100 Data presented show that the cover Adhesive C in combination with Chemlok 205 is heat stable up to at least 800C.

EXAMPLE 5

Steel plates are primed with Chemlok 205 and then coated with Adhesive D which has been stored at 280C for various times. Polychloroprene to steel test pieces are prepared by compression at 1600C for 20 minutes. Peel adhesion tests give the following results:

Storage time Peel Strength (NImm) (%) Freshly prepared 4 weeks 20 weeks is 14 100 14 100 Data presented illustrate the excellent shelf life of the Adhesive D.

16 EXAleLE 6 Steel plate is primed with Chemlok 205 and then coated with cover Adhesive B. One end of a 25 mm length of vulcanised polychloroprene test strip is coated with the same adhesive B. After drying, the coated steel and rubber are compressed together using a clamp. The whole assembly is heated in oven at 170 0 C for 20 minutes. After cooling, the test piece gives a peel strength of 12 Nlmm with 100% rubber failure. This result illustrates the suitability of Adhesive B for bonding vulcanised rubber to metal.

EXI"LE 7 The ends of two vulcanised polychloroprene test strips are coated with cover Adhesive D. After drying, the coated areas are compressed together using a clamp. The whole assembly is heated in oven at 170 0 C for 20 minutes. After cooling, the unit of bonded strips gives a peel strength of 10 NImm with 100% rubber failure. This result illustrates the suitability of Adhesive D for bonding vulcanised rubber to vulcanised rubber.

ELE 8 ENR (50 mole % epoxide) compounds as shown in Table 3.are prepared on a laboratory two-roll mill. Adhesion test pieces are 17 prepared by directly bonding these ENR compounds onto the gritblasted, unprimed steel plates at 170 0 C for 40 minutes. Peel strengths presented in Table 3 illustrate the enhanced adhesion of ENR compounds to metal when ENR is heated with benzoic acid and phenolic resin S? 154 respectively.

Table 3: Peel adhesion of ENR compounds to grit-blasted steel ENR (50 mole %Epoxide) 100 100 100 100 100 100 100 100 HAT 20 20 20 20 20 20 20 20 Benzoic acid 3 6 9 12 SP 354 resin 10 20 30 40 Peel adhesion (NImm) 3 7 12 13 2.1 2.4 3.4 4.4 Table 4: Peel adhesion of ENR compounds to grit-blasted steel Adhesive Composition D Alloprene Benzoic acid SP 154 resin 128.5 128.5 128.5 128.5 20 is 8 is Peel adhesion (N/mm) 1.6 3.7 5.2 25 Data presented in Table 4 illustrate the enhanced adhesion to metal when ENR compound is heated with chlorinated natural rubber (Alloprene). More significantly, a high adhesion to metal is achieved when ENR compound is heated in the presence of a combination of Alloprene, benzoic, acid and phenolic resin.

-it- 1EXAME 9 The primer Adhesive Composition ú is prepared by dissolving/dispersing the components listed in equal proportion of toluene and methyl ethyl ketone to achieve 2TIo total solid content.

Adhesive ú Parts by weight Adhesive composition B (dry) Chlorinated NR (Alloprene) Phenolic resin (SP 154) Benzoic acid so so The steel plates are primed with Adhesive B and then coated with either cover Adhesive B, Chemlok 220 or Cilbond 58.

NR, and CR compounds are each bonded onto such coated plates a t 160 0 C for 20 minutes. Peel adhesion tests give the following res ul ts:

Cover Adhesive Rubber Compound Peel Adhesion Rubber Failure N /= (%) ENR Adhesive B CR 13.5 100 Chemlok 220 CR 11.5)00 NR 10 100 Cilbond 58 CR 10)00 NR 8 100 1.9 Data presented illustrate the effectiveness of ENR primer Adhesive E in combination with ENR cover Adhesive B and also with commercial cover adhesives.

EXAMPLE 10

Polychloroprene compound to metal test pieces are prepared using the primer Adhesive E in combination with the cover adhesive, Chemlok 220. Peel adhesion tests are carried out at 80 0 C and at 23 0 C after the test pieces are subjected to boiling water for 2 hours.

Peel Adhesion Rubber Failure Test Condition Rubber Compound (Nlmm) (%) At 800C NR 7 100 CR 8.5 100 At 230C NR 8.5 100 (After boiling water, 2 hours) CR 13 100 Data presented illustrate that the primer Adhesive B is heat stable and resistant to boiling water.

EXAMPLE 11

Primer Adhesive E is used in combination with cover Adhesive. B to bond polychloroprene compound to steel, brass and aluminium respectively. The adhesion is effected at 1600C for 20 minutes. Peel adhesion tests give the following results:

A0 v tal Peel Adhesion Rubber Failure (N Imm) (%) Steel 13.5 100 Brass 14 100 Aluminium 9 100 Data presented illustrate the versatility of the primer Adhesive E with different metallic substrates.

EXAMPLE 12

Adhesive Compositions F,G and H are prepared by dissolving/ dispersing the components listed in equal proportion of toluene and methyl ethyl ketone to achieve W1o total solid content.

Adhesive (Parts by weight) F G Adhesive Composition B (dry) 100 Adhesive Composition D (dry 100 Chlorinated NR (Alloprene) so so a Phenolic resin (SP 154) so so is Benzoic acid 16 16 5 Adhesives F,G and B are each used as a single coat adhesive to bond polychloroprene and hypalon compounds to steel at 16 0 0 C for 20 minutes. Peel adhesion tests give the following results:

21 Adhesive Rubber Compound Peel Adhesion Rubber Failure (Nlmm) (%) CR 11 100 Hypalon 16 100 G CR 14.5 100 Hypalon 19 100 CR 14 100 Hypalon is 100 Data presented illustrate that the ENR adhesives F,G and H are good single coat adhesives for bonding chlorinated polymers such as polychloroprene and hypalon to metals.

EM.TLE 13 The ENR Adhesive F is used in combination with the primer, Chemlok 205, to bond various chlorinated and polar rubber compounds onto steel at 160 0 C for 20 minutes. Peel adhesion tests give the following results:

Rubber Compound Peel Adhesion Rubber Failure (NImm) (%) CR 13.5 100 Hypalon 15.5 100 NBR 12.5 100 Polyurethane 17 100 22 Data presented illustrate that Adhesive P is also an excellent cover adhesive for bonding chlorinated and other polar rubbers to metals.

ELE 14 Polychloroprene compound to steel test pieces are cured at 160 0 C for 20 minutes using a combination of Chemlok 205 and cover Adhesive H. They are then exposed to various environmental conditions as summarised in Table 5. Peel adhesion of the test pieces are tested before and after the environmental exposure.

Table 5: Environmental tests on Adhesive H as cover,coat Conditions Peel Adhesion Rubber Failure (N /m) (%) None 14 100 Water at 28 0 C, 7 days 18 100 Boiling water, 2 hours 14 100 5% RC1 at 280C, 7 days 17 100 5% NaOH at 280C, 7 days 16 100 5% NaCl, aerated at 28 0 C, 7 days 18 100 AST.4 No 3 oil at 100 0 C, 3 days 5 100 Data presented illustrate that the adhesive H has good resistance to various environmental conditions.

A 1 EXAMPLE 15

The bondability of the Adhesive H as a single coat in. polychloroprene to steel is measured after storing the Adhesive at 28 0 C for 5 months. No loss of adhesion is observed in comparison with the freshly prepared adhesive. The result illustrates the excellent storage life of the Adhesive H.

EXAMPLE 16

Vulcanised polychloroprene is bonded to vulcanised. polychloroprene using the Adhesive H as described in example 7. The unit of bonded strips gives a peel adhesion of 11 N1mm with 100Z rubber failure. This illustrates the suitability of Adhesive H for bonding vulcanised rubber to vulcanised rubber.

EXAMPLE 17

ENR (50 mole % Epoxide) ENR (25 mole % Epoxide) Carbon black (RAF) Chlorinated NR (Alloprene) Phenolic resin (SP 154) Benzoic acid Sulphur 1 Adhesive (Parts by weight) 25 100 8 is 100 A it The adhesives I J are prepared by dissolving /dispersing the components in equal proportion of toluene and methyl ethyl ketone to achieve 40Z total solid content. The adhesives 1 and J are each used in combination with Chemlok 205 to bond NR, SBR, PB, ENR, M.M and CR compounds onto steel at 160 0 C for 20 minutes. Peel adhesion tests give the following results:

Adhesive Rubber Compound Peel Adhesion Rubber Failure (NImm) (%) 1 I NR 13 100 I SBR 11 so I PB 4 100 I ENIR 9 90 (25 mole Z Epoxide) I NBR 8.5 40 1 CR 9 100 j NR 14 100 j SBR 14 100 j PB 4 100 j ENR 14 100 (25 mole % Epoxide) j NBR 13 so j CR is 100 Data presented show that the Adhesives I and J are suitable for bonding both the Don-polar and polar rubbers to metal.

1 úXMPLú to Adhesive (Parts by weight) K ENR (50 mole % Epoxide) ENR (25 mole % Epoxide) Carbon black ORF) Chlorinated U, (Alloprene) Phenolic resin (SP 134) Sulphur 30 20 30 15 150 1 The Adhesive K is prepared by dissolving /dispersing the empaiffts in e4jal proportion of toluene and methyl ethyl ketone to achieve 207,.. total solid content. A variety of vulcanised rubbers are bonded to the same or other compositions using Adhesive K as described in example 7. Peel adhesive tests give the following results.

Rubber to rubber Peel adhesive Failure (N/mm) (%) NR/NR 16 100 CR/CR 10 100 IMR ICR 12 100 SBRISBR 9 100 b N1 BRINBR 9 100 Data presented illustrates the suitability of Adhesive X for bonding vulcanised rubbers to themselves, or to other vulcanised rubber compositions.

EXAMPU 19 The adhesive X is used as a single coat to bond MR and polychloroprene compounds to steel at 1606C for 20 minutes. Peel adhesive tests give the following results Rubber Peel adhesive Failure (NIMM) (%) HR 14 100 CR 9 100 Hypalon is - 1 nn __ Data presented shows that the M Adhesive X can be used as a single coat to bond polar and ton-polar rubbers to metal.

4 3.

6.

Claims

A method of bonding a first substrate formed of a polar polymeric material to a second substrate formed of a metal having a primer coating thereon, which method comprises applying to at least one of said first and second substrates a layer of an adhesive composition comprising epoxidised natural rubber with an epoxide content in the range of from 1 to 90 mole % and,optionally, a filler in an amount of upto 100 parts by weight per 100 parts by weight of the epoxidised natural rubber, bringing the said first and second substrates into intimate contact and maintaining the substrates in contact with each other while bonding occurs.

A method according to claim 1, wherein the adhesive composition is applied in the form of a solution of the epoxidised natural rubber in an organic solvent.

A method according to claim 2, wherein the total solids content of the solution is in the range of from 15 to 40% by weight.

4, A method according to any one of claims 1 to 3, wherein the epoxidised natural rubber has an epoxide content of about 50 mole %.

5. A method according to any one of claims 1 to 4, wherein the filler is present in an amount of from 10 to 50 parts by weight per 100 parts by weight of the epoxidised natural rubber.

A method according to any one of claims 1 to 5, wherein the filler is selected from carbon black, hydrated silica and their mixtures.

A method according to any one of claims 1 to 6, wherein the adhesive composition also contains a curing agent for the epoxidised natural rLbber.

R 1 27 - 9.

A method according to claim 7, wherein the cure system consists of sulphur and common rubber accelerators such as thiazoles and sulphenamides.

A method of bonding a first substrate formed of a polar polymeric material to a second substrate formed of a polar polymeric material or of a metal which method comprises applying to at least one of said first and second substrates a layer of an adhesive composition, bringing the said first and second substrates into intimate contact and maintaining the substrates in contact with each other while bonding occurs wherein the adhesive composition comprises epoxidised natural rubber with an epoxide content in the range of from 1 to 90 mole % and, optionally, a filler in an amount of up to 100 parts by weight per 100 parts by weight of the epoxidised natural rubber and also at least one of the following:- i) a carboxylic acid in an amount of from 1 to 30 parts by weight per 100 parts by weight of the epoxidised natural rubber; ii) a chlorinated polymer in an amount of from 1 to 300 parts by weight per 100 parts by' weight of the epoxidised natural rubber; and iii) a phenolic resin in an amount of from 1 to 300 parts by weight per 100 parts by weight of the epoxidised natural rubber.

10. A method according to claim 9, wherein the carboxylic acid is benzoic acid present in an amount of from 5 to 20 parts by weight per 100 parts by weight of the epoxidised natural rubber.

A method according to claim 9, wherein the phenolic resin is a heat reactive phenolic resin I 28 - present in an amount of from 10 to 150 parts by weight per 100 parts by weight of epoxidised natural rubber.

12. A method according to claim 9, wherein the chlorinated polymer is chlorinated natural rubber present in an amount of from 10 to 150 parts by weight per 100 parts by weight of the epoxidised natural rubber.

13. The use as a primer adhesive for metal substrates,of a composition comprising epoxidised natural rubber having an epoxide content in the range of from 1 to 90 mole % and, optionally, a filler in an amount of up to 100 parts by weight per 100 parts by weight of the epoxidised natural rubber, and at least one of:- (i) a carboxylic acid in an amount of from 1 to 30 parts by weight per 100 parts by weight of the epoxidised natural rubber, ii) a chlorinated polymer in an amount of from 1 to 300 parts by weight per 100 parts by weight of the epoxidised natural rubber, and iii) a phenolic resin in an amount of from 1 to 300 parts by weight per 100 parts by weight of the epoxidised natural rubber.

15.

14. The use of the composition according to claim 13, wherein the carboxylic acid is benzoic acid present in an amount of from 5 to 20 parts by weight per 100 parts by weight of the epoxidised natural rubber.

The use of the composition according to claim 13, wherein the phenolic. resin is a heat reactive phenolic resin present in an amount of from 10 to 150 parts by weight per 100 parts by weight of the epoxidised natural rubber.

z S; 1 - 29 16. The use of the composition according to claim 13, wherein the chlorinated polymer is chlorinated natural rubber in an amount of from 10 to 150 parts by weight per 100 parts by weight of the epoxidised natural rubber.

17. A composition comprising epoxidised natural rubber having an epoxide content of from 1 to 90 mole %, optionally a filler in an amount of upto 100 parts by weight per 100 parts by weight of the epoxidised natural rubber and further comprising sulphur in an amount of from 10 to 60% of the total solids content of the composition.

A composition according to claim 17, wherein the sulphur is present in an amount of from 25 to 507o of the total solids content of the adhesive composition.

19. A composition according to claim 17 or claim 18, which further comprises at least one of:- 18.

i) a carboxylic acid in an amount of from 1 to 30 parts by weight per 100 parts by weight of the epoxidised natural rubber, ii) a chlorinated polymer in an amount of from 1 to 300 parts by weight per 100 parts by weight of the epoxidised natural rubber, and iii) a phenolic resin in an amount of from 1 to 300 parts by weight per 100 parts by weight of the epoxidised natural rubber. 20. A composition according to claim 19, wherein the carboxylic acid is benzoic acid in an amount of from 5 to 20 parts by weight per 100 parts by weight of the epoxidised natural rubber. 21. A composition according to claim 19, wherein the phenolilb resin is a heat reactive phenolic resin in k A- - It 22.

25.

an amount of from 10 to 150 parts by weight per 100 parts by weight of the epoxidised natural rubber. A composition according to claim 19, wherein the chlorinated polymer is chlorinated natural rubber in an amount of from 10 to 150 parts by weight per 100 parts by eight of the epoxidised natural rubber. 23. A method of bonding a first substrate formed of a polar or a non-polar polymeric material to a second substrate formed of a polar or a non-polar polymeric material or of a metal, optionally having a primer coating thereon which method comprises applying to at least one of said first and second substrates a layer of a composition according to any one of claims 17 to 22, bringing the said first and second substrates into intimate contact with each other and maintaining the substrates in contact with each other while bonding occurs. 24. A method according to claim 23 wherein the first substrate is formed of a non-polar rubber material selected from natural rubber, styrenebutadiene rubber and polybutadiene and the second substrate is formed of a metal. A method according to claim 23, wherein the first substrate is formed of a non-polar rubber material selected from patural rubber, styrene-butadiene rubber and polybutadiene and the second substrate is formed of a non-polar rubber material selected from natural rubber, styrene-butadiene rubber and polybutadiene.

Published 1990 at The Patent Office, State House, 56f7l High Holborn, London WClR 4TP. Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques Itd, St Mary Cray, Kent, COM 1/87 1