JPS6017318B2 - Adhesive for fluoro rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive for fluororubber, and more specifically, to a specific modified fluorocarbon rubber.

This invention relates to a fluororubber adhesive made of elastomer. Propylene-tetrafluoroethylene copolymers and vinylidene fluoride-propylene hexafluoride copolymers are known as crosslinkable or dilutable fluoroelastomers that exhibit excellent heat resistance and chemical resistance. . A heat-resistant and chemical-resistant fluororubber is produced by blending a vulcanization aid, a reinforcing agent, a filler, etc. with the fluoroelastomer, which is usually used in It is used as a product for various purposes. Applications that take advantage of the heat and chemical resistance and rubber elasticity of fluororubber include packing for various chemical equipment, gaskets, etc.

For example, gaskets for plate-type heat exchangers are promising applications for fluororubber, but this type of gasket can be larger than 1×0.5. Therefore, when such large packings, gaskets, etc. are attached to various devices, the gaskets are likely to become misaligned during the attachment process, resulting in problems such as breakage. In general,
This problem can be avoided by using hydrocarbon grease as an adhesive to temporarily secure the gasket.
However, when using a fluororubber gasket or the like, general-purpose grease or the like deteriorates significantly during use, making it impossible to take advantage of the excellent properties of fluororubber. According to research conducted by the present inventors, adhesives for plates and gaskets are used when attaching fluororubber gaskets to metal plates, etc., but no adhesive has been found that is practically satisfactory.

Therefore, the required functions for such adhesives include workability during application (adhesive at room temperature to about 100 qo and sufficient adhesive strength), workability during gasket replacement (ease of peeling) It is considered that the performance of the adhesive for fluororubber (acid resistance, alkali resistance, heat resistance, steam resistance, etc.) is sufficient. From the above-mentioned viewpoint, the present inventor has conducted various studies and examinations in order to provide a pressure-sensitive adhesive for fluororubber that can be used in practical applications. It has been found that a low molecular weight fluoroelastomer obtained by thermally decomposing an elastomer in the presence of oxygen satisfies the above-mentioned required functions.

Thus, the present invention has been completed based on the above knowledge, and it is possible to obtain a number average molecular weight of 5,000 to 8 by heating a fluoroelastomer above the thermal decomposition temperature in the presence of oxygen.
The present invention provides a new adhesive for fluororubber made of a modified fluoroelastomer.

Since the adhesive of the present invention is based on a fluoroelastomer, it has sufficient heat resistance and chemical resistance, and since the molecular weight is within a specific range due to thermal decomposition treatment, it has good adhesion to fluororubber. The force is suitable, and the workability during pasting or replacement is good.

Furthermore, as is clear from the preferred embodiments described below, the adhesive of the present invention can be prepared in the form of an appropriate organic solvent solution, and is useful for improving the various workability described above. In the present invention, the modified fluoroelastomer is
Specification No. 1-83973 (Japanese Patent Publication No. 55-41641), Specification
It can be easily obtained by the method described in Japanese Patent Publication No.-5724. That is, the adhesive of the present invention is produced by heat-treating a fluoroelastomer having a number average molecular weight of 20,000 or more at a thermally decomposable temperature of 250 to 450°C in the presence of oxygen for 15 minutes or more and within a range that maintains a specific molecular weight. A modified fluoroelastomer as an agent is obtained. Therefore, such thermal modification treatment may be carried out with the addition of a small amount of basic oxide such as magnesium oxide, lead oxide, calcium oxide, or zinc oxide. 66290 (Japanese Unexamined Patent Publication No. 54-1385), etc., the adhesive of the present invention may be dried under reduced pressure at a temperature that does not cause thermal decomposition after heat treatment. The fluoroelastomer that is the base of the fluororubber and the fluoroelastomer that is the base of the adhesive of the present invention are preferably used when pasting on a metal base material such as a stainless steel plate. The type is not particularly limited, and a wide range of examples may include those that are well-known or well-known. Typically, fluorophostomers made of addition polymers such as propylene-tetrafluoroethylene copolymers and vinylidene fluoride-hexafluoropropylene copolymers can be suitably exemplified in the present invention. Then,
Suitable propylene-tetrafluoroethylene copolymer elastomers include, in addition to the main components of tetrafluoroethylene and propylene, components that can be copolymerized with these, such as ethylene, isobutylene, acrylic acid, and alkyl esters thereof. Propylene containing an appropriate amount of ster, methacrylic acid and its alkyl ester, vinyl fluoride, pinylidene fluoride, propylene hexafluoride, chloroethyl vinyl ether, chlorotrifluoroethylene, alkyl vinyl ether, perfluoroalkyl vinyl ether, etc. - It may be a tetrafluoroethylene copolymer. The molar ratio of tetrafluoroethylene and propylene constituting the copolymer, the molar ratio of other components added as necessary, and the molecular weight of the copolymer are determined based on the target material to be treated. It can be arbitrarily selected depending on the usage, heat and chemical resistance elastomer properties, ease of acquisition, etc. For example, in the present invention, the molar ratio of ethylenenopropylene tetrafluoride is 99/1 to 10/9, preferably 95/5 to 30/70, considering the excellent heat resistance that is a characteristic of the copolymer. Especially from 90/10 to 45/5
Propylene-tetrafluoroethylene based copolymers such as No. 5 can be widely used. The content of the above-mentioned components other than the main components of tetrafluoroethylene and propylene may be about 0 to 50 mol%, preferably about 0.5 to 40 mol%. Further, as for the molecular weight of the copolymer, it is usually desirable to employ a copolymer having a molecular weight of about 5 or more, and a copolymer having a moderately high molecular weight can provide advantageous applicability. For example, 70,000 or more, preferably 10 to 25
A propylene-tetrafluoroethylene copolymer having a molecular weight of about Also, suitable vinylidene fluoride
In addition to the main components of vinylidene fluoride and propylene hexafluoride, the hexafluorinated propylene copolymer elastomer also contains components that can be copolymerized with these, such as tetrafluorinated ethylene, perfluorovinyl ether, It may also contain an appropriate amount of acrylic acid and its alkyl ester, metharylic acid and its alkyl ester, etc.

The molar ratio of vinylidene fluoride/propylene hexafluoride is 95.
Vinylidene fluoride-propylene hexafluoride copolymers with a ratio of /5 to 40/6Q, preferably 90/10 to 60 to 40, are widely used, and tetrafluoroethylene, perfluorovinyl ether, etc. have a ratio of 0 to 40 Mol%, preferably 10~
It may be copolymerized in an amount of about 30 mol%. The molecular weight of the copolymer (b) is preferably as high as possible, 50,000 or more, for example 70,000 or more, especially 10 to 2
Approximately 5 directions are adopted. When the high molecular weight fluoroelastomer as described above is heated at its thermally decomposable temperature in the presence of oxygen,
For example, in air for 15 minutes to 4 hours, preferably 30 minutes.
The modified fluoroelastomer used as the adhesive of the present invention is obtained by heat treatment for a period of minutes to 24 hours.

When heat-treating with the addition of a basic oxide, an addition ratio of about 0.01 to 5 parts by weight, preferably about 0.1 to 3 parts by weight per 100 parts by weight of fluoroelastomer may be adopted. . In addition, the vacuum drying conditions after the heat treatment include a temperature of room temperature to 2000C, a time of 15 minutes to 48 hours, especially a time of 3 minutes to 2 hours, and a degree of vacuum of 10 degrees Hg or less, preferably 50 degrees Hg or less. may be adopted. In the adhesive of the present invention, it is important that the fluoroelastomer is thermally decomposed in the presence of oxygen to reduce its molecular weight. The objects and effects of the present invention cannot be achieved with low molecular weight fluoroelastomers. Also,
Modified fluoro as adhesive. The molecular weight of the elastomer is
It is important that the number average molecular weight is in the range of about 5,000 to 80,000, preferably about 20,000 to 60,000. If the molecular weight of the modified fluoroelastomer is too large, the adhesive strength will be low, and if the molecular weight is too small, the adhesive will wash away during heating, which is not preferred in practice. The adhesive of the present invention has a relative adhesive strength of 0.3 to 1.5k9 as defined below.
It is preferably 0.5 to lk9/low.

Here, relative adhesive strength is defined as follows. In other words, 25 x 60 x 2 (thickness) skin stainless steel (SUS27
) Apply sample adhesive to the sheet to a thickness of 50 to 100A,
Press the fluororubber Karosulfur sheet with a pressure of 100qo x 10k9'. For example, the following fluororubber calosulfate sheets are employed. C2F4/C3day6 content molar ratio 55
/45 tetrafluoroethylene/propylene copolymer with a molecular weight of 80,000 to 200,000, and MT-carbon, organic peroxide, triallylysocyanurate, etc.
Parts by weight, 1 to 2 parts by weight, and 1 to 5 parts by weight were blended and press vulcanized at 150 to 180 oo for 40 to 10 minutes. Therefore, regarding crimped products, 23
A 90 degree peel test is carried out at 5 degrees per minute, the peel load (kg)/2.5 skin is measured, and the relative adhesive strength is expressed in units of k9' arc. The adhesive of the present invention may be in the form of sheeting a specific modified fluoroelastomer by roll molding, press molding, etc., but it may also be in the form of usually dissolving the modified fluoroelastomer in a suitable solvent.

In the case of sheeting, the thickness can be varied depending on the purpose of use and the object to which it is applied, but it is usually 0.1.
~1 leg, especially about 0.2 to 0.5 legs may be adopted. Of course, such a sheeting form may be processed into an appropriate shape depending on the shape of the target packing, gasket, etc., for example. In the case of a solution form, it is desirable that the concentration of the modified fluoroelastomer is 1% by weight or more, usually 10 to 5% by weight, particularly 15 to 3% by weight. will be adopted. If the concentration of the modified fluoroelastomer is too low, there will be difficulty in imparting sufficient adhesive strength. A wide range of solvents can be used as long as they can dissolve the modified fluoroelastomer, but fluorinated chlorinated saturated hydrocarbon solvents are preferred in consideration of safety, workability, and other considerations. be. In particular, ethane trifluoride and trichloride is preferred from the viewpoint of solubility, ease of handling, safety, etc. of the modified fluoroelastomer.
The adhesive of the present invention can be used between a fluororubber and a base material.

The method of applying the adhesive is not particularly limited, and for example, coating, spraying, or casting of an adhesive solution may be employed, or if the base material is a fiber cloth, dipping, impregnation, etc. may be employed. Furthermore, when using an adhesive sheet, it may be placed between the fluororubber and the base material and laminated. The coating method can be applied to either or both of the fluororubber and the base material.
When an adhesive solution is used, it is dried after application, and the fluororubber and the base material are bonded together via the adhesive layer. Of course, dry pressure bonding may be performed at the same time. Usually room temperature to 100℃
At a temperature of 0.1~50k9/ground, preferably 1~
It can be easily crimped with a pressure of about 20k9/swim. The adhesive of the present invention is a fluoroelastomer, but since its purpose is adhesive, it is not necessarily necessary to mix a vulcanizing agent, a vulcanizing aid, or other additives, but rather a vulcanizing agent. It is preferable not to use vulcanization aids or vulcanization aids.

That is, even if these are used, it is desirable that the amount of the organic peroxy compound be 1 part by weight or less and the organic polyallylic compound be 3 parts by weight or less per 100 parts by weight of the modified fluoroelastomer. Furthermore, when blending fillers such as Q-alumina, aerosil silica, and kaolin, 4 parts by weight or less are employed based on 100 parts by weight of the modified fluoroelastomer. Incidentally, additives such as pigments, antioxidants, and stabilizers may be appropriately added and blended as long as they do not impede the performance of the adhesive of the present invention. The adhesive of the present invention is suitably employed when affixing fluororubber to various base materials.

The types of fluoroelastomers that serve as the base of the fluororubber can be exemplified in a wide range as described above. Depending on the type of fluoroelastomer, it is converted into a vulcanizate by the action of a chemical vulcanizing agent, ionizing radiation, etc., using an appropriate vulcanization mixture, and becomes a fluororubber product. For example, a chemical vulcanizing agent consisting of an organic peroxy compound can be used, and specific examples include diacyl peroxide such as dibenzoyl peroxide, dicumyl peroxide, di-t-
Butyl peroxide, t-butyl peroxide acetate, t-butyl peroxyisopropyl carbonate,
Monobaroxy compounds such as baroxyesters such as t-butylperoxybenzoate, and 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexyne-3,2,5-dimethyl- 2.5-di-(t-butylperoxy)-para-diisopropylbenzene, 2.
5-dimethyl-2,5-di-(benzoylperoxy)
Examples include diveroxy compounds such as -hexane. These may be used alone or in a mixture of two or more. The amount of the chemical vulcanizing agent used is usually 0.1 to 20 parts by weight per 100 parts by weight of the fluoroelastomer.
Preferably, about 1 to 10 parts by weight may be employed. Also,
Eisei Bridge can be formed by irradiation with ionizing radiation such as Q-rays, B-rays, Y-rays, neutron beams, accelerated particle beams, X-rays, and electron beams.

Usually, y-rays from cobalt-60, accelerated particle beams, electron beams, etc. are preferred. For example, 1-1 B X-ray/
At the same time, ionizing radiation is irradiated at a dose rate of about 1 to 5 x 107 roentgens/hour, and the irradiation dose is in the range of 1 to 1 rad, especially about 1 to 5 x 1 rad. By doing so, a fluoroelastomer made of a propylene-tetrafluoroethylene polymer can be converted into a crosslinked product. Therefore, it is possible to irradiate ionizing radiation in air, and the irradiation atmosphere must be kept in a vacuum or under an air flow such as argon, helium, nitrogen, etc., or even kept in water. I can also do things. The crosslinking reaction caused by irradiation with ionizing radiation proceeds efficiently even at room temperature or about room temperature, so there is no need to limit the irradiation temperature, and it is also possible to adopt an irradiation temperature below room temperature, about 100°C, or more. be. In crosslinking using amines, so-called alkyl polyamines such as hexamethylene diamine, tetraethylenebentamine, and triethylenetetramine, or their salts such as carbamic acid and cinnamylidene acid, or piperazine, piverizine, pyridine,
Aromatic polyamines such as aniline and phenanthroline and their salts, as well as reagents using Schiff's base and having nucleophilic properties such as hydroquinone, bisphemer A, and catechol, and their alkali metal salts, ammonium salts, etc. It is also possible to use them in combination as appropriate with straight mirror polyethers such as polyethylene glycol and polypropylene glycol, cyclic polyethers, quaternary ammonium salts, quaternary phosphonium salts, and the like as auxiliaries.

When vulcanizing a fluoroelastomer, a conventionally known or well-known vulcanization aid may be used in combination with either the method using ionizing radiation irradiation or the method using a chemical vulcanizing agent.

For example, vulcanization aids such as allyl compounds, sulfur, organic amines, maleimides, methacrylates, and dipinyl compounds may be employed. Preferably diallyl phthalate,
Organic polyallylic compounds such as triallyl phosphate, triallyl cyanurate, triallyl isocyanurate, diallylmelamine, and para-penzoquine/endioxime, P.P.
Oxime compounds such as '-dibenzoylbenzoquinone dioxime are used, and organic polyallylic compounds are particularly preferred. The amount of the vulcanization aid added may be about 0.1 to 2 parts by weight, preferably about 0.2 to 1 part by weight, based on 100 parts by weight of the fluoroelastomer. When vulcanizing the above-mentioned vulcanization compound, various additives normally used in the subsequent vulcanization method of fluorine-containing elastomer may also be added and blended during the vulcanization of the fluoroelastomer. obtain.

These additives include metal oxides such as magnesium oxide and lead oxide, reinforcing agents such as carbon black and fine silica, other fillers, pigments, antioxidants, stabilizers, and the like. When the various additives mentioned above are incorporated in the vulcanization of fluoroelastomers, it is desirable to mix the chemical vulcanizing agent, vulcanization aid, and other additives sufficiently and uniformly.

This mixing may be carried out using conventionally used rubber twill rolls, Banbury mixers, or the like.
Working conditions during mixing are not particularly limited, but usually 30~
By kneading for about 10 to 60 minutes at a temperature of about 80 DEG C., the additives can be sufficiently dispersed and mixed into the fluoroelastomer. It goes without saying that various other additives may be mixed during the kneading, or may be added and mixed before or after kneading. Note that it is desirable that the working conditions and operations during mixing be carried out by selecting optimal conditions depending on the types and purposes of the raw materials and ingredients used. In the case of vulcanization of a fluoroelastomer, conventionally used operations may be employed for heating and vulcanizing with a chemical vulcanizing agent.

For example, an operation may be employed in which the vulcanized compound is heated while being pressurized, or an operation in which the vulcanized compound is heated in a heating furnace or steam cauldron may be employed. It is desirable to select the optimum working conditions during heat vulcanization depending on the raw materials and formulation used. The temperature during heating and vulcanization is usually about 80 to 250 oo,
Preferably, about 120 to 200 oo may be adopted. Further, the heating time is not particularly limited, but is selected in the range of 3 minutes to 3 hours, preferably in the range of 5 minutes to 2 hours, depending on the chemical additive. The heating time can be shortened by increasing the heating temperature. Note that reheating treatment after vulcanization can also be employed and is useful for improving physical properties. For example, 1
Reheating treatment at a temperature of 50 to 25,000 ℃, preferably 180 to 23,000 ℃ for about 0.5 to 2 hours may be employed. In the present invention, it is desirable to select the adhesive depending on the type of fluororubber, that is, it is preferable to use a modified rubber of fluoroelastomer, which is the base of the fluororubber, and the adhesive of the fluororubber.

For example, when attaching a fluororubber gasket made of a propylene-tetrafluoroethylene copolymer elastomer to a stainless steel plate, it is necessary to attach a fluororubber gasket made of a pyrolyzed modified propylene-tetrafluoroethylene copolymer elastomer to a stainless steel plate. For example, choosing an adhesive. The adhesive of the present invention is
Since the base is a specific modified fluoroelastomer,
It can be advantageously employed in applications aimed at heat resistance, chemical resistance, steam resistance, food safety, etc.

Examples of specific uses include the following.
For example, it can be used when attaching a heat exchange gasket (plate gasket) of a milk sterilizer to a stainless steel plate for heat exchange. In this case, it is important that the fluororubber gasket is properly set on the plate. If the gasket were to protrude from a predetermined location on the plate, the seal would be defective. In order to set correctly, the adhesive between the gasket and the plate requires a strong adhesive force. Further, it is desirable that the gasket does not come off from the plate when the plates are periodically peeled off and inspected.

In this respect, it is also important that the adhesive has a high adhesive strength. However, when inspecting the gasket by peeling it off, it is required that the adhesive strength be reduced by 4 mm and that no adhesive remains on the plate. The present invention can fully meet these seemingly contradictory demands. It is self-evident that since the main ingredient is an elastomer based on tetrafluoroethylene-propylene, it can exhibit properties such as acid resistance, heat resistance, steam resistance, and food safety at the same time. In addition, adhesives containing small amounts of peroxide and triallyl isocyanurate are
Since it can be used as a strong adhesive between the vulcanized fluororubber sheet and metal when heated, it can be used as a post-adhesive for lining. Next, examples of the present invention will be described in more detail, but it goes without saying that the present invention is not limited by the above description.

The "peel strength" used in the examples is measured as follows. That is, a fluororubber and a base material were bonded together using an adhesive, a sample was prepared that complied with the JIS K6301 peel test, and the peel strength (unit: kg/kg) was measured.
Measured as 180 degree peel strength. Cut the laminated sample pieces into pieces with a diameter of 25.0 mm and a length of 0.5 mm, and a length of 10 m or more.
Peel off one end of this test piece by hand and attach it to the chuck of the tensile tester. At this time, make sure that the angle between the layer to be peeled and the layer to be peeled is approximately 180 degrees. The tensile speed of the test piece is 50.0±2.5 sides/min. The number of test piece samples is 2 or more, and the peeling load is expressed as the average value of the peeling of each test piece (the maximum value of the tensile load curve is taken as the value), and the adhesion strength (peeling strength) is calculated using the following formula. do. TF = Hard TF: Adhesion strength (k9/skin) F: Peeling load (k9) b: Medium test piece (reduced) Example 1 Average molecular weight 180,000, C2F4/C3HB content molar ratio 5
5/45 propylene-tetrafluoroethylene copolymer,
A modified fluoroelastomer having an average molecular weight of 40,000 is obtained by heat treatment at 360° C. for 2 hours in an electric furnace in an air atmosphere.

The modified fluoroelastomer was rolled to a thickness of 0.2 with a cooling roll.
As a side sheet, dissolve it in ethane trifluoride and trichloride to a concentration of 5.
% by weight of the solution. Stainless steel sheet (SUS27
) was coated with the adhesive solution, and a fluororubber vulcanized sheet was pressure-bonded thereon with a 10020 x 10k9' base. The peel strength of the obtained laminated sheet was 1 kg/arc. The fluororubber vulcanized sheet is as follows. That is, the average molecular weight was 100,000, and the molar ratio of C2F4/C3day6 was 55/45. Parts by weight of MT-carbon 8 in pyrene-tetrafluoride copolymer (Afras ■150),
Blending 1 part of Beloximone F-100, 5 parts of triallylysocyanurate, and 2 parts by weight of sodium stearate,
Pre-caro vulcanization (primary vulcanization) was performed for 160 pm x 30 minutes. Next, the temperature was raised stepwise at (160°C x 1 hour), 180°C x 1 hour, and 200qo x 2 hours, and oven vulcanization was performed to obtain a vulcanized sheet. Apply this adhesive to the plate gasket (SUS2) of the actual milk sterilizer.
7 stainless steel plate and the fluororubber carbon sulfur sheet) using steam at about 140°C.
Although it was used for a long time, no deterioration was observed. Furthermore, it was easy to remove the fluororubber gasket and clean the stainless steel plate with ethane trifluoride and trichloride. Example 2 As a fluoroelastomer, 340q of a British polymer with a molar ratio of vinylidene fluoride/propylene hexafluoride/ethylene tetrafluoride of 60/25/1 and a molecular weight of 130,000 were used.
A modified fluoroelastomer was obtained by heat treatment in air for 5 hours.

Claims (1)

[Scope of Claims] 1. An adhesive for fluororubber comprising a modified fluoroelastomer having a number average molecular weight of 5,000 to 80,000 obtained by heating a fluoroelastomer to a temperature above the thermal decomposition temperature in the presence of oxygen. 2 The modified fluoroelastomer is a propylene-tetrafluoroethylene copolymer elastomer having a number average molecular weight of 30,000 or more, which is heated at 250 to 450°C for 15 minutes to 48°C in the presence of oxygen.
The adhesive for fluororubber according to claim 1, which is heat-treated for a period of time. 3. A patent in which the modified fluoroelastomer is obtained by heat-treating a vinylidene fluoride-propylene hexafluoride copolymer elastomer having a number average molecular weight of 50,000 or more at 250 to 450°C for 15 minutes to 48 hours in the presence of oxygen. Claim 1
Adhesive for fluororubber as described in section. 4. The adhesive for fluororubber according to claim 1, which is in the form of a sheeting having a thickness of 0.1 to 1 mm. 5. The adhesive for fluororubber according to claim 1, which is in the form of a solution having a modified fluoroelastomer concentration of 10% by weight or more. 6. The adhesive for fluororubber according to claim 5, wherein the solvent in the form of a solution is trifluorotrichloride ethane. 7 For 100 parts by weight of modified fluoroelastomer,
The adhesive for fluororubber according to claim 1, which employs a blending ratio of 1 part by weight or less of an organic peroxy compound, 3 parts by weight or less of an organic polyallylic compound, and 40 parts by weight or less of a filler.