Method of surface treating and laminating a fluorine resin

Abstract: The invention relates to a laminate, which has at least a portion where a fluorine resin and a crosslinking elastic adhesive body such as of an ethylene-vinyl acetate copolymer or the like are directly bonded together and which is used as a window material of buildings or mainly used as an outdoor electric member and also to a method for making the laminate. More particularly, the invention provides a surface-treating method of a fluorine resin suited to impart bonding properties to a fluorine resin for the laminate, to a laminate having a good property of bonding between the fluorine resin and the crosslinking elastic adhesive body, and also to a method for making such a laminate as mentioned above.

Description: This invention relates to a laminate, which has, at least at a part thereof, a portion where a fluorine resin and a crosslinking elastic adhesive body, such as of an ethylene-vinyl acetate copolymer or the like, are directly bonded to each other and which may be useful as a window material for buildings and an electric member mainly for outdoor use and also, to a method for making such a laminate. More particularly, the invention relates to a method for the surface treatment of a fluorine resin, which is suited to impart bonding properties to a fluorine resin for the laminate, a laminate having an excellent property of bonding between the fluorine resin and the crosslinking elastic adhesive body, and a method for making such a laminate as mentioned above. The laminate obtained by directly bonding, to a fluorine resin, a crosslinking elastic adhesive body, such as of an ethylene-vinyl acetate copolymer (EVA) or the like, is used by bonding to the surface of a building material or a solar cell for surface protection, impartment of a stain resistance, sealing and the like. In this case, the performance of bonding between the fluorine resin and the crosslinking elastic adhesive body required in view of an applied environment includes, aside from storage stability, a heat resistance after bonding via crosslinkage and weatherability such as a resistance to ultraviolet light. To ensure strong bonding with a crosslinking elastic adhesive body, the fluorine resin is subjected to a variety of surface treatments prior to the bonding. As the surface treatment method, there are known a sodium treatment, a sand blast treatment, a flame treatment, a corona treatment, a plasma treatment, a sputter etching treatment, a radiation irradiation treatment, and the like. Of these, the corona treatment is able to produce, on the fluorine resin surface, various types of functional groups that contribute to imparting good bonding properties thereto and is thus known as an effective treating method. However, the fluorine resin surface treated by these treating methods may be unsatisfactory, in some cases, with respect to its bonding force, thus the best use being not made of the surface-treating effect at present. JP11222530 describes a method for making a fluorine resin coated wire having adhesive property by plasma treatment. JP1110807 describes a method for making a laminate of an ethylene vinyl acetate copolymer and a fluorine resin in which the fluorine resin is subjected to corona discharge treatment in accordance with the preambles of claims 1 and 4. Under these circumstances in the art, it would be desirable to provide one or more of: a method for the surface treatment of a fluorine resin, which is suitable for reliably making a laminate obtained by direct and strong bonding between a fluorine resin and a crosslinking elastic adhesive body, such as of an ethylene-vinyl acetate copolymer or the like, and also a method for making a laminate; the provision of a laminate in which a fluorine resin and a crosslinking elastic adhesive body, such as of an ethylene-vinyl acetate copolymer or the like, are directly, strongly bonded together and which is excellent in initial bonding property and storage stability, and also of a method for making the laminate. The present inventors have made intensive studies, and as a result, found methods (1) and (2) set out below, a fluorine resin treated by the methods, and a method for making a laminate having the fluorine resin therein. (1) A method for subjecting a fluorine resin surface to corona discharge treatment in an atmosphere of a nitrogen gas while controlling the concentration of an oxygen gas to 4 to 150 ppm. (2) A method for carrying out a thermal treatment after having subjected a fluorine resin surface to corona discharge treatment in air. With respect to the method (1) it has been found that when a fluorine resin is subjected to corona discharge treatment in a nitrogen gas while controlling the concentration of an oxygen gas in the nitrogen gas at 4 to 150 ppm, the property of bonding between the fluorine resin and the crosslinking elastic adhesive body and storage stability are drastically improved. Moreover, when the crosslinking elastic adhesive body, mainly composed of an ethylene-vinyl acetate copolymer, is directly laminated and integrally combined with the fluorine resin surface-treated under the oxygen concentration conditions, the fluorine resin and the crosslinking elastic adhesive body are strongly bonded together, thus making it possible to reliably produce a laminate that is excellent in storage stability and has good properties such as a surface protecting property, a stain resistance, a high transparency, a member-sealing property and the like. With respect to the method (2), it has been found that a fluorine resin is subjected to corona discharge treatment in air and is subsequently thermally treated, thereby improving the property of bonding with the crosslinking elastic adhesive body. In addition, when the thus treated fluorine resin is directly laminated to and integrally combined with a crosslinking elastic adhesive body, mainly composed of an ethylene-vinyl acetate copolymer or the like, the fluorine resin and the crosslinking elastic adhesive body are bonded together to reliably obtain a laminate that is demanded to have various properties such as a stain resistance, a high transparency, sealing properties and the like. The invention has been accomplished based on these findings. According to claim 1 of the invention, there is provided a method for making a laminate wherein a fluorine resin, which consists of an ethylene-tetrafluoroethylene copolymer, and a crosslinkable elastic adhesive body, mainly composed of an ethylene vinyl acetate copolymer, are directly bonded together, which method comprises the steps of treating the fluorine resin surface with corona discharge in an atmosphere of nitrogen gas, laminating the crosslinkable elastic adhesive body to the fluorine resin surface and crosslinking the crosslinkable elastic adhesive body, characterised in that the concentration of oxygen gas in said atmosphere is controlled in the range 4 to 150 ppm. Preferably, the concentration of oxygen gas is controlled in the range 4 to 50 ppm. According to claim 4 of the invention, there is provided a method for making a laminate wherein a fluorine resin, which consists of an ethylene-tetrafluoroethylene copolymer, and a crosslinkable elastic adhesive body, mainly composed of an ethylene vinyl acetate copolymer, are directly bonded together, which method comprises the steps of treating the fluorine resin surface with corona discharge in an atmosphere, laminating the crosslinkable elastic adhesive body to the fluorine resin surface and crosslinking the crosslinkable elastic adhesive body, characterised in that said atmosphere is air and in that the method comprises the step of subsequently treating the fluorine resin surface thermally. The thermal treatment is preferably effected at 80 to 300°C for 5 to 60 minutes. DETAILED EMBODIMENTS OF THE INVENTION The invention is now described in detail. The surface-treating method of a fluorine resin, is a surface treatment for strongly bonding a fluorine resin and a crosslinking elastic adhesive body. The fluorine resin is treated by one of the following methods (1) to (2): (1) a method wherein the fluorine surface treatment is subjected to corona discharge treatment while controlling a concentration of an oxygen gas in an atmosphere of nitrogen gas ranges from 4 to 150 ppm; and (2) a method wherein the fluorine resin surface is treated with corona discharge in air and subsequently thermally treated. The fluorine resin treated according to one of the methods (1) to (2) is an ethylene-tetrafluoroethylene copolymer (ETFE). In the practice of the invention, an ethylene-tetrafluoroethylene copolymer is used, which is thermoplastic in nature and is excellent in moldability, heat resistance, resistance to chemicals, electric characteristics (dielectric characteristic), non-adhesiveness, abrasion resistance, cut-through resistance, radial ray resistance, UV transmission, IR absorptivity and the balance of these characteristic properties. Accordingly, the copolymer can be conveniently used as a surface material for outdoor electric members. The treating method (1) is one wherein a fluorine resin can be strongly bonded to a crosslinking elastic adhesive body and is imparted with a good bonding property along with good storage stability. In the treating method (1), when the fluorine resin is subjected to corona discharge treating under given conditions, it is necessary to control a concentration of an oxygen gas in a nitrogen gas atmosphere at a given very low level. The oxygen concentration is in the range of 4 to 150 ppm, preferably 4 to 100 ppm, and more preferably 4 to 50 ppm. If the oxygen concentration is less than in the above range, storage stability becomes worsened when a laminate is fabricated. On the other hand, when the concentration exceeds the range, an initial bonding force considerably lowers. The procedure of controlling the oxygen gas concentration at a very low level includes those methods including, for example, a method, in which a nitrogen gas is blown, at an atmospheric pressure, against a portion where corona discharge takes place, a method, in which a corona discharge portion is covered with a polymer sheet or the like, and after sealing, an inner gas is replaced by nitrogen gas, and a combination thereof. Gases other than oxygen are limited to nitrogen gas, and the treatment can be carried out inexpensively without involving a danger. In this case, even if air remains slightly, any trouble is not given provided that the oxygen concentration is controlled within a range of 4 to 150 ppm. It will be noted that the oxygen concentration can be measured, for example, by galvanic cell type densitometer. According to the treating method (1) of the present invention, corona discharge may be processed at an atmospheric pressure without any specific conditions except that the procedure has to take place under the above-mentioned atmosphere where the oxygen concentration is very low. According to the surface-treating method (1), the treated fluorine resin is imparted with bonding property to a crosslinking elastic adhesive body and also with storage stability, so that the treating method of a fluorine resin according to the invention can be conveniently adopted as a surface-treating method of a fluorine resin employed as a pretreatment upon bonding of a crosslinking elastic adhesive body with a fluorine resin. Furthermore, the surface-treating method of a fluorine resin of (2) is a treating method of a fluorine resin to be strongly bonded to a crosslinking elastic adhesive body and also a surface-treating method including a combination of a corona discharge treatment and a thermal treatment. The surface-treating method of (2) comprises subjecting a fluorine resin to a corona discharge treatment wherein the corona discharge treatment is effected by use of air, not a nitrogen gas, and an ordinary corona treating apparatus that is used for treatment in air can be employed as it is. For performing corona discharge in air, it is preferred to carry out the treatment as uniformly as possible in such a way that air is blown against a discharge port to invariably send fresh air thereto, but the method is not limited to this. In the practice of the invention, the fluorine resin subjected to corona discharge is further thermally treated. Accordingly, the bonding property to a crosslinking elastic adhesive body described hereinlater is reliably imparted. The thermal treating conditions of the invention are not critical, and it is recommended that a known device, such as a precise oven, a drying furnace, an IR lamp or the like, is used for treatment at 80 to 300°C, preferably 100 to 180°C, for a time of 5 to 60 minutes, preferably 10 to 30 minutes. As described hereinabove, the fluorine resin treated according to the method (2) of the invention is improved in the property of bonding to a crosslinking elastic adhesive body, and the corona treatment is carried out by use of air, and can thus be performed inexpensively. As set out above, the surface-treating methods (1) to (2) of a fluorine resin according to the invention are able to reliably impart, to the treated fluorine resin, the property of strong bonding to a crosslinking elastic adhesive body. Accordingly, these methods can be conveniently adopted as a surface-treating method of a fluorine resin for pretreatment in bonding of a crosslinking elastic adhesive body to obtain a laminate, which is used as a window material of buildings or the like or an outdoor electric member. Next, a method for making a laminate for achieving the first object of the invention comprises subjecting a desired type of fluorine resin to one of fluorine resin surface-treating methods (1) to (2) and directly bonding a crosslinking elastic adhesive body to the resultant fluorine resin. To obtain the crosslinking adhesive body, there is beneficially used an ethylene-vinyl acetate copolymer composition, in which there is conveniently used one having a vinyl acetate content ranging from 5 to 50 wt%, preferably from 10 to 45 wt%. Where the copolymer composition is used as a sealing material, it may be used in the form of a sheet. It is preferred that after attachment to a fluorine resin, the copolymer composition is crosslinked and integrally formed of the fluorine resin. Accordingly, the crosslinking elastic adhesive body composition includes a thermal and/or photocurable crosslinking elastic adhesive body composition formulated with an organic peroxide and/or a photosensitizer. The composition may be formulated, from the standpoint of bonding property with an acryloxy group-containing compound, a metharyloxy group-containing compound, an allyl group-containing compound, a silane coupling, an epoxy group-containing compound, a hydrocarbon resin or the like. For instance, for the thermal curing of the ethylene-vinyl acetate copolymer, an organic peroxide may be added to. The organic peroxide may be any ones provided that they are able to decompose at a temperature of 70°C or over and generate radicals. Preferably, those compounds having a half-life period of 10 hours and a decomposition temperature of 50°C or over are used. Usable organic peroxides include, for example, 2,5-dimethylhexane-2,5-dihydro peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne-3, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane, dicumyl peroxide, α,α'-bis(t-butyl peroxyisopropyl)benzene, n-butyl-4,4'-bis(t-butyl peroxy)valerate, 1,1-bis(t-butyl peroxy)cyclohexane, 1,1-bis(t-butyl peroxy)-3,3,5-trimethylcyclohexane, t-butyl peroxybenzoate, t-butyl peroxyacetate, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5-bisperoxybenzoate, butyl hydroperoxide, p-methane hydroperoxide, p-chlorobenzoyl peroxide, t-butyl peroxyisobutyrate, hydroxyheptyl peroxide, chlorohexanone peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, cumyl peroxyoctoate, succinic acid peroxide, acetyl peroxide t-butyl peroxy(2-ethylhexanoate), m-toluoyl peroxide, benzoyl peroxide, 2,4-dichlorobenoyl peroxide and the like. These may be used singly or in admixture of two or more. In general, the peroxide is used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the copolymer. When a photosensitizer is added for photopolymerization of an ethylene-vinyl acetate copolymer, it is preferred to use a radical photopolymerization initiator as the photosensitizer. Among radical photopolymerization initiators, there are mentioned, as a hydrogen-withdrawal-type photopolymerization initiator, such as, for example, benzophenone, methyl orthobenzoylbenzoate, 4-benzoyl-4'-methyldiphenyl sulfide, isopropylthioxanthone, diethylthioxanthone, ethyl-4-(diethylamino)-benzoate and the like. There are mentioned, as an intramolecular cleavage-type initiator, benzoin ether, benzyl dimethyl ketal and the like, as an α-hydroxyalkylphenone type initiator, 2-hydroxy-2-methyl-1-phenylpropan-1-on, 1-hydroxycyclohexyl phenyl ketone, an alkylphenyl glyoxylate, diethoxy acetophenone, and the like, and as an α-aminoalkylphenone type initiator, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanon-1 and the like. Alternatively, acylphosphine oxide may also be used. These may be used singly or in admixture of two or more as the photosensitizer. The amount ranges from 0.1 to 10 parts by weight per 100 parts by weight of the copolymer. Aside from the photosensitizer, organic peroxides may be further formulated, if necessary, by which thermal curing may be used in combination with photocuring. Moreover, as set forth hereinabove, at least one of an acryloxy group-containing compound, a methacryloxy group-containing compound and an allyl group-containing compound may be added to the copolymer. Examples of the acryloxy and methacryloxy group-containing compounds used for this purpose include acrylic acid or methacrylic acid derivatives, e.g. esters of the acids. The alcoholic residues of the esters include, aside from an alkyl group having from 1 to 24 carbon atoms, preferably from 1 to 18 carbon atoms, e.g. a methyl group, an ethyl group, a dodecyl group, a stearyl group and a lauryl group, a cycloalkyl group having from 3 to 6 carbon atoms, e.g. a cyclohexyl group, substituted alkyl groups (whose alkyl moiety has from 1 to 24 carbon atoms, preferably from 1 to 18 carbon atoms) including halogen-substituted, hydroxyl group-substituted and amino group-substituted alkyl groups such as a tetrahydrofurfuryl group, an aminoethyl group, a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 3-chloro-2-hydroxypropyl group and the like, and glycidyl groups. Moreover, there may be likewise used esters with polyfunctional alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol and the like. The allyl group-containing compounds include, for example, diallyl phthalate, diallyl fumarate, diallyl cyanurate, triallyl isocyanurate, triallyl cyanurate and the like. These compounds may be used on their own or in admixture of two or more, and the amount is sufficient to be 50 parts by weight or below per 100 parts by weight of the copolymer and is generally in the range of 0.1 to 50 parts by weight, preferably from 0.5 to 20 parts by weight. For the purpose of improving the quality of the resin, a silane coupling agent may be formulated. The silane coupling agents used for this purpose may be known ones including, for example, γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyl triethoxysilane, vinyl tris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyl triacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and the like. These silane coupling agents is generally used in an amount of 10 parts by weight or below per 100 parts by weight of the copolymer, preferably from 0.01 to 10 parts by weight, and more preferably from 0.01 to 5 parts by weight. The crosslinking elastic adhesive body formulated with the silane coupling agent is enabled to be directly bonded to a fluorine resin subjected to the surface treatment, especially, to a fluorine resin subjected to corona discharge treatment. As will be stated hereinafter, it is preferred that to permit stronger bonding to the surface-treated fluorine resin, the formulated adhesive body is not directly bonded to the fluorine resin but is bonded, as a second crosslinking elastic adhesive layer or body, to the fluorine resin through a first crosslinking elastic adhesive layer or body formulated with little or no silane coupling agent. This will be described in more detail. The crosslinking elastic adhesive body composition may further comprise an epoxy group-containing compound other than epoxy silane as a bonding promoter. Examples of the epoxy group-containing compound include triglycidyltris(2-hydroxyethylene) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexandiol glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, phenol polyoxyethylene (5 moles) glycidyl ether, p-t-butylphenyl glycidyl ether, adipic acid diglycidyl adipate, glycidyl o-phthalate ester, glycidyl methacrylate, butyl glycidyl ether and the like. A similar effect may be obtained using an alloyed polymer containing an epoxy group. These epoxy group-containing compounds may be used singly or in admixture of two or more, and the amount is generally in the range of 0 to 20 parts by weight, preferably from 0.1 to 20 parts by weight, per 100 parts by weight of the copolymer. A hydrocarbon resin may also be added to the copolymer in an amount of from 0 to 200 parts by weight, preferably from 5 to 150 parts by weight, and more preferably from 10 to 100 parts by weight, per 100 parts by weight of the copolymer. The hydrocarbon resin may be a natural resin or a synthetic resin. For natural resins, rosins, rosin derivatives and terpene resins are preferably used. Gum resins, tall oil resins, wood resins and the like are used as the rosin. Usable rosin derivatives include those of rosins that are hydrogenated, disproportionated, polymerized, esterified, and converted to metal salts. Terpene resins include, aside from terpene resins such as α-pinene, β-pinene and the like, terpenephenol resins. As other natural resins, there may be used dammar, copal and shellac. On the other hand, synthetic resins preferably include petroleum resins, phenolic resins, xylene resins and the like. As the petroleum resin, there may be used aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, hydrogenated petroleum resins, pure monomer-based petroleum resins, coumarone-indene resins and the like. Phenol resins include alkylphenol resins, modified phenol resins and the like. Xylene resins include xylene resin, modified xylene resins and the like. Aside from the additives mentioned above, antioxidants, dyes, processing aids, UV absorbers and the like may be further added. The crosslinking elastic adhesive body composition can be formed as a film with a desired width and thickness by weighing predetermined amounts of the copolymer, a curing agent (organic oxide and/or photosensitizer), a silane coupling agent, an acryloxy group, methacryloxy group or allyl group-containing compound, uniformly mixing by means of a kneading machine such as a roll mill or a kneader, and subjecting to a film-forming device such as a calender roll, a T-die extruder or an inflation die. The film thickness preferably ranges from 1 to 1000 µm, more preferably from 5 to 800 µm. The thus film-formed composition layer is laminated with a fluorine resin, subjected to surface treatment according to one of the methods (1) to (2), according to a lamination method using, for example, a hot press to integrally combine them together. In this case, the thermal curing of an ethylene-vinyl acetate copolymer depends on the type of organic oxide and it is preferred to heat at a temperature of 70 to 170°C, preferably from 70 to 150°C, for a time of 2 to 60 minutes, preferably from 5 to 30 minutes. It is preferred from the standpoint of bonding property that curing is effected by heating under a pressure of 1 to 5000 kPa, preferably from 10 to 2000 kPa. On the other hand, with photocuring, a laminate can be cured by irradiation with UV light such as from a mercury lamp. To shorten the curing time and improve the hardness, UV light may be irradiated while preliminarily heating the laminate at 40 to 120°C. The laminate obtained by the method of the invention is used, for example, as a window material such as of buildings or an outdoor electric member. In the case, for the fabrication of the laminate, the steps other than the step of directly bonding a fluorine resin and a crosslinking elastic adhesive body can be performed in a usual manner. EXAMPLE The invention is more particularly described by way of examples, which should not be construed as limitation thereof. Comparative examples are also described. Examples 1 to 5 and Comparative Examples 1 to 3 The following ethylene-tetrafluoroethylene copolymer film (100 µm in thickness) was provided as a fluorine resin film and subjected to corona discharge treatment according to the following procedure. Fluorine resin film Neoflon ETFE EF-0100, made by Daikin Ind. Co., Ltd. Corona discharge treatment The discharge electrodes (with a width of 30 cm) of a corona discharge device were covered with an acrylic resin container, under which while a nitrogen gas was passed at a rate of 10 liters/minute, the concentration of an oxygen gas in the container was controlled at levels indicated in Table 1. The treatment was carried out by use of a power supply of Model HV05-2, made by Tantec Inc., at a corona output of 250 W at a film feed rate of 1 mm/minute. Next, the thus corona discharge-treated fluorine resin films were, respectively, laminated with a film (500 µm) of an ethylene-vinyl acetate copolymer composition having the following formulation. A 100 µm thick polyester film was laminated on a side of the ethylene-vinyl acetate copolymer composition film opposite to the side laminated with the fluorine resin, followed by hot pressing at 150°C for 15 minutes at 1000 kPa to cure the film and integrally combine them together. Ethylene-vinyl acetate copolymer composition Ultracene 634 100 parts by weight Triallyl isocyanurate 2 γ-Methacryloxypropyltrimethoxysilane 0.5 1,1-Bis(t-butyl peroxy) 3,3,5-trimethylcyclohexane 2 The resultant laminates were each subjected to measurement of a bonding force, as an initial bonding force, by means of Autograph (AGS-100D), made by Shimadzu Corporation. On the other hand, the laminates made by the above method were stored over one month under the same conditions and their bonding force was measured in a similar manner to calculate, as storage stability, a ratio of the bonding force after passage one month to the initial bonding force. In this case, the storage stability of 80% or over was judged as acceptable or ○, and a lower value was judged as ×. The results are shown in Table 1. For comparison, laminates were made in the same manner as described above except that the concentration of oxygen at the time of the corona treatment of the fluorine resin film was outside the range of the invention. The laminates were measured and evaluated with respect to the initial bonding force and bonding force after one month. The results are also shown in Table 2. Oxygen concentration (ppm) Initial bonding force (N/25mm) Bonding force after one month (N/25mm) Storage stability (%) Judgment Comparative Example 1 2 54 39 72 × Example 1 4 52 43 83 ○ Example 2 9 51 43 84 ○ Example 3 28 54 44 81 ○ Example 4 35 53 46 87 ○ Example 5 134 43 35 81 ○ Comparative Example 2 460 42 29 69 × Comparative Example 3 20% 15 - - × Example 6 and Comparative Example 4 The following ethylene-tetrafluoroethylene copolymer film (100 µm in thickness) was provided as a fluorine resin film and, after corona discharge treatment by the following method, was thermally treated. Fluorine resin film Neoflon ETFE EF-0100, made by Daikin Ind. Co., Ltd. Corona discharge treatment The discharge electrodes (with a width of 30 cm) of a corona discharge device were covered with an acrylic resin container, under which air was passed at a rate of 10 liters/minute at an atmospheric pressure. The treatment was carried out by use of a power supply of Model HV05-2, made by Tantec Inc., at a corona output of 250 W at a film feed rate of 1 mm/minute. Thermal Treatment A fine oven (DF-61) serving as a thermal treating device and made by Yamato Science Co., Ltd., was used to thermally treat the corona-discharged ETFE at 150°C for 30 minutes. Next, an ethylene-vinyl acetate copolymer composition film (500 µm in thickness) was laminated to the thus corona discharged fluorine resin film, and a 100 µm thick polyester film was further laminated to a side of the ethylene-vinyl acetate copolymer composition film opposite to the side laminated with the fluorine resin film. Thereafter, the film was cured by means of a hot press at 150°C for 15 minutes at a compression pressure of 1000 kPa to make an integral combination. Ethylene-vinyl acetate copolymer composition Ultracene 634 100 parts by weight Triallyl isocyanurate 2 γ-Methacryloxypropyltrimethoxysilane 0.5 1,1-Bis(t-butyl peroxy) 3,3,5-trimethylcyclohexane 2 The resultant laminate was subjected to measurement of bonding force by use of Autograph (AGS-100D), made by Shimadzu Ltd. The results are shown in Table 2. For comparison, a laminate was made in the same manner as set out above except that the fluorine resin was subjected to corona treatment in air but was not thermally treated, followed by measurement of bonding force. The results are also shown in Table 2. Thermal treating time (minutes) Bonding force (N/25mm) Example 6 30 41 Comparative Example 4 0 3

Claims: A method for making a laminate wherein a fluorine resin, which consists of an ethylene-tetrafluoroethylene copolymer, and a crosslinkable elastic adhesive body, mainly composed of an ethylene vinyl acetate copolymer, are directly bonded together, which method comprises the steps of treating the fluorine resin surface with corona discharge in an atmosphere of nitrogen gas, laminating the crosslinkable elastic adhesive body to the fluorine resin surface and crosslinking the crosslinkable elastic adhesive body, characterised in that the concentration of oxygen gas in said atmosphere is controlled in the range 4 to 150 ppm. A method according to claim 1 wherein said concentration of oxygen gas is controlled in the range 4 to 50 ppm. A method according to Claim 1 wherein the crosslinkable elastic adhesive body is crosslinked by means of a radical initiator. A method for making a laminate wherein a fluorine resin, which consists of an ethylene-tetrafluoroethylene copolymer, and a crosslinkable elastic adhesive body, mainly composed of an ethylene vinyl acetate copolymer, are directly bonded together, which method comprises the steps of treating the fluorine resin surface with corona discharge in an atmosphere, laminating the crosslinkable elastic adhesive body to the fluorine resin surface and crosslinking the crosslinkable elastic adhesive body, characterised in that said atmosphere is air and in that the method comprises the step of subsequently treating the fluorine resin surface thermally. A method according to claim 4 wherein said thermal treatment is effected at 80 to 300 °C for 5 to 60 minutes. A method according to Claim 4 wherein the crosslinkable elastic adhesive body is crosslinked by means of a radical initiator.

Inventors: KOBAYASHI TAICHI, SAITOH SHINJI, YOSHIKAWA MASATO, KOBAYASHI, TAICHI, SAITOH, SHINJI, YOSHIKAWA, MASATO
Applicants: BRIDGESTONE CORP, BRIDGESTONE CORPORATION
Application year: 2000
Main classification: B29C59
IPC codes: B32B27, B29C71, B29C59