JPH0768502B2 - Adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an adhesive composition containing a modified polyolefin resin dispersed in an organic solvent and useful as an adhesive between metal and polyolefin. More particularly, the present invention relates to an adhesive composition having good coating properties by a roll coater and excellent adhesiveness, and a production method capable of economically producing the composition.

(Prior Art) A carboxyl group-modified polyolefin resin is known as an adhesive between metal and polyolefin. In order to produce this modified polyolefin resin, a mixture of an ethylenically unsaturated carboxylic acid such as maleic anhydride or a radical polymerizable monomer containing an ethylenically unsaturated carboxylic acid in the presence of a radical generator is added to the polyolefin resin. Allow graft reaction. As a typical modification method, there are known a method in which a polyolefin resin raw material is melted and kneaded with a radically polymerizable monomer to react, and a method in which a polyolefin resin is dissolved in an organic solvent and reacted in a solution state. The former method can produce the modified resin economically advantageously because it does not use an organic solvent, but it has a drawback in production that the control of the graft reaction is difficult, and unreacted monomers are mixed as impurities. Inevitably, the adhesive strength is poor, and there are hygienic problems due to the presence of impurities. Therefore, the adhesive obtained by this method cannot be applied to food container applications.

The method of graft-reacting a radical-polymerizable monomer in a state in which a polyolefin resin raw material is dissolved in an organic solvent is easy to control the reaction, but still there is an unreacted monomer or a polymer of a monomer that does not contribute to grafting. Therefore, the problems of adhesiveness and hygiene still remain. For this reason, Japanese Patent Publication No. 60-225 and Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent No. 63911, it is necessary to separate the modified resin from the organic solvent and then wash it with an organic solvent to remove these impurities. However, a large amount of organic solvent is used for this purpose, and the modified polyolefin resin obtained by this method is limited in terms of economy, although it is excellent in performance.

On the other hand, as a method of applying a carboxyl group-modified polyolefin resin adhesive to a substrate such as a metal plate, a method of applying the modified resin in a molten state, electrostatic powder coating as a powder coating, or fluidized dipping coating is used. Although a method, a method of fusing as a sheet-like material, and the like are known, these methods require a special device and are uneconomical because the adhesive layer is unavoidably thicker than necessary. Therefore, it has been proposed that the modified polyolefin resin is made into a dispersion in an organic solvent, and this composition is applied to a substrate by a coating device such as a roll coater. However, the composition in which the modified polyolefin resin is simply a dispersion of an organic solvent has a drawback that the coatability is extremely poor. For this reason, JP-A-53-
As disclosed in Japanese Patent No. 13342, it has been proposed to improve the coatability of the composition by blending a soluble resin such as an epoxy resin. According to this technique, the coatability of the adhesive composition is improved and an adhesive having good performance can be obtained, but the problem of economical efficiency due to the need for cleaning treatment of the modified resin still remains. Was there.

(Problems to be Solved by the Invention) The present invention provides an economically advantageous adhesive composition that eliminates the need for washing with an organic solvent in producing a carboxyl group-modified polyolefin resin.

Further, the present invention provides an adhesive composition having good coating suitability by a roll coater.

Furthermore, the present invention provides an adhesive composition that firmly adheres between a metal and a polyolefin.

Furthermore, the present invention provides an adhesive composition having excellent hygiene properties that contains almost no monomer impurities.

[Structure of Invention]

(Means for Solving the Problems) In the present invention, a polyolefin-based resin dissolved in an organic solvent is mixed with maleic anhydride or maleic acid and a styrene-based monomer in substantially equimolar amounts in the presence of a radical generator. The present invention relates to an adhesive composition obtained by graft-modifying the modified resin solution and precipitating fine particles of the modified resin from the resulting modified resin solution, and a method for producing the adhesive composition.

The polyolefin resin in the present invention means a homopolymer of ethylene or propylene, an ethylene-propylene copolymer or ethylene or propylene and other olefins such as 1-butene, 1-pentene, 1-hexene, 1
-Heptene, 1-octene, 4-methyl-1-pentene, 1-
Includes decene copolymers. Further, a copolymer of an olefin and a different monomer such as an ethylene-vinyl acetate copolymer can be used as the polyolefin resin.

The radical generator in the present invention is a normal radical polymerization initiator, and refers to a substance that generates an active radical that can be easily decomposed by heat, light or the like to initiate polymerization. Persulfates such as ammonium persulfate as peroxide system,
Hydroperoxides such as hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, 2,
Peroxyketals such as 2-bis (t-butyl peroxide) octane, dicumyl peroxide, t-butyl cumyl peroxide, dialkyl peroxides such as di-cumyl peroxide, octanoyl peroxide, deca Diacyl peroxides such as noyl peroxide, lauroyl peroxide and benzoyl peroxide, di-isopropyl peroxycarbonate, di (2
-Ethylhexyl) peroxide carbonate and other peroxide carbonates, t-butyl peroxyisobutyrate, t-butyl peroxybenzoate and other peroxy esters, 2,2'-azobisisobutyronitrile and other azo compounds , Copper, iron powder-benzyl chloride mixture, redox initiator by combination of oxidizing agent and reducing agent,
Further, a metal alkyl, a combination of a metal alkyl and an oxygen donor or a metal halide, or an organometallic compound such as an alkyl peroxy metal can be used. These radical generators are selected according to the conditions such as the organic solvent used in the graft reaction and the reaction temperature. In the present invention, the temperature at which the polyolefin resin is dissolved in the organic solvent to carry out the graft reaction, for example, 100 to 150 ° C. A half-life of about 1 minute is suitable for benzoyl peroxide, lauroyl peroxide, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butylperoxy (2 -Ethylhexanoate), 2,2'-azobisisobutyronitrile and the like are preferable.

The amount of the radical generator used in the present invention is 0.5 to 5 parts, preferably 1 to 3 parts, based on 100 parts of the polyolefin resin used.

The organic solvent used in the present invention is a solvent which is capable of dissolving a polyolefin resin under heating and performing a graft reaction, and which is suitable for precipitating fine particles of the modified resin from the obtained modified resin solution. is there. Such organic solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone,
Aromatic hydrocarbons such as benzene, toluene, xylene, and other alkylbenzenes, cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, esters such as methyl cellosolve acetate, butyl cellosolve acetate, ethyl acetate, butyl acetate, and isopropyl. Alcohols, butyl alcohol, diacetone alcohol, and other alcohols are appropriately selected, and if necessary, a mixed solvent thereof is used.

In the present invention, the polyolefin resin is heated and dissolved in an organic solvent to carry out a graft modification reaction. The proportion of the polyolefin resin and the organic solvent used is 1 to 25% by weight, preferably 1 to 15% by weight, as the concentration of the modified polyolefin resin at the end of the graft reaction. When the proportion of the polyolefin resin used is too high, the concentration of the reaction solution becomes high, the graft reaction becomes non-uniform, and when fine particles of the modified resin are precipitated from the modified resin solution after the reaction,
The composition becomes a gel and cannot be applied to the substrate.

The monomers to be graft-modified with the polyolefin resin in the present invention are maleic anhydride or maleic acid and a styrene monomer. Examples of the styrene-based monomer include styrene, α-methylstyrene, chlorostyrene, cyanostyrene, aminostyrene, hydroxystyrene, vinyltoluene and divinylbenzene.

The amounts of maleic anhydride or maleic acid and the styrenic monomer used are substantially equimolar, and the range is such that the molar ratio of the styrenic monomer to maleic anhydride or maleic acid is 0.8 to 1.1, preferably 0.9. ~ 1.05
Is. The total amount of the monomers used is 0.25 to 50 parts, preferably 3 to 40 parts, based on 100 parts of the polyolefin resin used. When the amount of the monomer used is more than 50 parts, a large amount of a polymer of the monomer that does not contribute to the graft modification is generated, and the adhesive strength tends to be reduced.

As a method for graft-modifying the polyolefin resin in the present invention, the polyolefin resin, maleic anhydride, styrene and a radical generator are added to an organic solvent such as xylene and heated to dissolve and react the polyolefin resin. Alternatively, there is a method in which a polyolefin resin, maleic anhydride and styrene are heated and dissolved in an organic solvent, and a radical generator is added at a constant rate at a constant temperature. This method keeps the radical concentration in the reaction system constant. It is effective for More specifically, for example, 40 to 100 parts by weight of xylene and 1 to 20 parts by weight of a polyolefin resin such as polypropylene, and a total of 0.05 to 10 parts by weight of maleic anhydride or maleic acid and a styrenic monomer in a substantially equimolar amount. Was added and dissolved at 130 ° C.
The solution dissolved in 0 part by weight is added dropwise over 1 hour, and after the addition, the reaction is completed by stirring for 1 hour.

The adhesive composition according to the present invention can form a resin dispersion by cooling the modified resin solution obtained by the above graft reaction while stirring and precipitating fine particles of the modified resin. Further, when depositing the fine particles of the modified resin, it is also an effective method to add another organic solvent or to add the modified resin solution into the other organic solvent while stirring.

In the present invention, a soluble resin can be added to the dispersion of the modified resin obtained by the above method to further improve the coatability and the adhesive performance. As these soluble resins, those soluble in a resin dispersion solution and having adhesiveness with a graft-modified polyolefin resin after being heated and dried are suitable. For example, an epoxy resin having a molecular weight of 1500 or more, an ethylene-vinyl acetate copolymer resin, an acrylic resin, a polyester resin, a benzoguanamine resin, a phenol resin, a urea resin, or the like, or a mixture thereof can be used. In particular, by combining and combining an epoxy resin and a curing agent resin of an epoxy resin such as a phenol resin or an amino resin, it is possible to further improve the coatability of the composition and improve the corrosion resistance of the metal substrate. . The amount of soluble resin that can be blended is not more than 10 times, preferably not more than 5 times that of the modified polyolefin resin on a weight basis.

The soluble resin can be added by adding it to the reaction solution during the graft reaction, adding it after completion of the graft reaction and stirring and cooling, or by stirring the graft reaction solution in the soluble resin solution. There is a method of adding.

The adhesive composition of the present invention is applied to a substrate such as a metal, and when the modified polyolefin is polyethylene, the temperature is 150 to 200 ° C,
In the case of polypropylene, heat treatment is performed at a temperature of 180 to 220 ° C. to remove the organic solvent and the modified polyolefin resin is melted to form an adhesive layer. Examples of the base material include treated steel plates such as tin-free steel, various plated steel plates, aluminum plates, and copper plates. A roll coater can be used to coat the base material, but spray coating,
Other coating methods such as flow coating may be used. The thickness of the adhesive layer is 1 to 10 µ, preferably 3 to 5 µ.

The adhesive layer formed on the metal base material is manufactured by fusing a molten polyolefin resin or by pressing and heating the polyolefin film to produce a metal-polyolefin laminate. The temperature conditions for laminating the polyolefin film are 150 to 200 ° C for polyethylene and 180 to 200 ° C for polypropylene. The metal-polyolefin laminate thus obtained can be used as a material for packaging containers and the like. In addition, the adhesive composition of the present invention,
It can be used as an adhesive having a metal protective coating function for metal-plastic film composite containers and the like.

(Operation and Effect of the Invention) It is known that maleic anhydride or maleic acid and a styrene-based monomer form an alternating copolymer by radical polymerization.

In the present invention, since the polyolefin resin is graft-modified with maleic anhydride or maleic acid and a styrene monomer, it is considered that the graft chain of the alternating copolymer is formed. Therefore, unlike the graft modification with maleic anhydride or maleic acid, in which homopolymerization hardly occurs, the modified polyolefin resin of the present invention forms a graft chain with a long chain length, which increases the affinity for organic solvents, resulting in coatability. Are expected to be improved.

In the present invention, maleic anhydride or maleic acid and the styrene monomer are used in substantially equimolar amounts in the graft modification. Since both monomers react rapidly to form an alternating copolymer, the amount of unreacted monomer that adversely affects the adhesive strength is extremely small, and therefore,
The adhesive strength is great and there is no problem of hygiene due to unreacted residual monomer.

According to the method for producing an adhesive composition of the present invention, it is not necessary to wash the modified polyolefin-based resin with an organic solvent to remove unreacted monomers and the like, and thus to purify the modified polyolefin-based resin economically. A solvent dispersion of can be obtained.

(Examples) Hereinafter, the present invention will be described with reference to Examples. In the examples, "part" means "part by weight" and "%" means "% by weight".

Example 1 In a reaction vessel equipped with a stirrer, a cooler, a dropping tube, and a nitrogen introducing tube, 480 parts of xylene, 80 parts of polyethylene resin (Ultzex 30200J Mitsui Petrochemical Industry Co., Ltd.), and maleic anhydride 7.76. And styrene (8.24 parts) (styrene / maleic anhydride molar ratio 1.0; hereinafter, referred to as St / MAA = 1.0) were added and dissolved by heating, and kept at 130 ° C. A solution prepared by dissolving 240 parts of xylene and 0.8 part of benzoyl peroxide in this solution was added dropwise with stirring for 1 hour to carry out the reaction.
After dropping, the mixture was further stirred for 1 hour and then gradually cooled to room temperature with stirring to precipitate fine particles of the modified resin to obtain an adhesive composition.

Examples 2 and 3 In Example 1, the amounts of xylene, polyethylene, maleic anhydride, styrene and benzoyl peroxide added dropwise to the reaction vessel were changed as follows, and the other adhesive compositions were obtained in the same manner. .

Example 2 Example 3 Xylene 560 parts 240 parts Polyethylene 8 parts 160 parts Maleic anhydride 0.19 parts 38.8 parts Styrene 0.12 parts 41.2 parts Benzoyl peroxide 0.08 parts 8 parts St / MAA 1.0 1.0 Example 4 Change ethylene
An adhesive composition was obtained in the same manner except that 80 parts of butene-1 copolymer resin (Neozex 45200 manufactured by Mitsui Petrochemical Industry Co., Ltd.) was used.

Example 5 Instead of the polyethylene resin in Example 1, ethylene-
40 parts of butene-1 copolymer resin (Neozex 45200, manufactured by Mitsui Petrochemical Co., Ltd.) and 40 parts of ethylene-vinyl acetate copolymer (Novatech AP132E, manufactured by Mitsubishi Kasei Co., Ltd.) were used. An adhesive composition was obtained.

Examples 6 and 7 Adhesive compositions were obtained in the same manner as in Example 1 except that the amounts of maleic anhydride and styrene added to the reactor were changed as follows.

Example 6 Example 7 Maleic anhydride 8.65 parts 7.38 parts Styrene 7.34 parts 8.62 parts St / MAA 0.8 1.1 Example 8 A polypropylene resin (Chisso Polypro K1014, manufactured by Chisso Corporation) was used instead of the polyethylene resin in Example 1. An adhesive composition was obtained in the same manner.

Examples 9 and 10 The adhesive compositions of Examples 9 and 10 were obtained in the same manner as in Examples 1 and 8 except that 9.19 parts of maleic acid was used instead of maleic anhydride.

Example 11 An adhesive composition was obtained in the same manner except that 9.35 parts of α-methylstyrene (molar ratio of α-methylstyrene to maleic anhydride was 1.0) was used instead of the styrene used in Example 1.

Example 12 To 100 parts of the adhesive composition obtained in Example 2, 50 parts of a solution prepared by dissolving 50 parts of an epoxy resin (Epicoat 1009, manufactured by Yuka Shell Epoxy Co., Ltd.) in 50 parts of cyclohexanone was added and stirred to bond. An agent composition was prepared.

Examples 13 and 14 100 parts of the epoxy resin solution used in Example 12 was stirred at 50 ° C. or lower, and the solution was synthesized under the conditions of Examples 3 and 8 and the modified resin before being deposited 50 Parts were added to obtain adhesive compositions of Examples 13 and 14.

Comparative Examples 1 and 2 Adhesive compositions of Comparative Examples 1 and 2 were obtained under the same conditions except that styrene was not used in Examples 1 and 8.

Comparative Examples 3 and 4 To 100 parts of the modified resins obtained in Comparative Examples 1 and 2, 100 parts of methyl ethyl ketone was added to precipitate the modified resin, which was then filtered. Further, the filtered matter is mixed with 50 parts of methyl ethyl ketone to 5
It was washed repeatedly and dried. 90 parts of xylene was added to 10 parts of each of the dried modified resin, heated and dissolved, and then stirred and cooled to precipitate the modified resin to obtain adhesive compositions of Comparative Examples 3 and 4.

Comparative Example 5 6.84 parts of maleic anhydride and 9.16 of styrene in Example 1
Part (St / MAA = 1.26) was used, and graft modification was performed under the same conditions to obtain an adhesive composition.

Comparative Example 6 9.18 parts of maleic anhydride and 6.82 of styrene in Example 1
Part (St / MAA = 0.7) was used and graft modification was performed under the same conditions to obtain an adhesive composition.

Coating test and adhesion test Using the adhesive compositions obtained in the examples and comparative examples, 0.32 mm
0.2mm thick polyethylene film or polypropylene film immediately after coating with a natural roll coater to a thickness of approximately 5μ on 200 × 300mm test pieces of thick TEIN FREE STEEL (TFS) and immediately after drying at 180 ℃ for 3 minutes. Was thermocompression bonded with a rubber roll. With respect to the adhesive compositions of the comparative examples, coating by flow coating was also used because of poor coating suitability. The adhesive strength of the TFS-polyolefin film laminated steel sheet thus created and the well shape at 5 mm intervals were carved with a knife from the film and processed by an Erichsen test of 7 mm, and this was further heated in boiling water for 5 hours. After the immersion, the adhesiveness of each was observed. The results are shown in Table 1.

The symbols and terms used in Table 1 are explained below.

Coatability A: Applicability as good as normal paint B: A little inferior to A but roll-coatable C: Almost no roll-coating Laminated film PE: Polyethylene film PP: Polypropylene film I-type Erichsen No irregularities: Well-shaped ridges cannot be exposed by forced peeling Peeling: Well-shaped ridges are easily peeled off As is clear from Table 1, the adhesives of Comparative Examples 1 and 2 show almost no adhesive force under normal conditions, but are compared. The adhesives of Examples 3 and 4 showed adhesive strength leading to film breakage, and showed that unreacted substances and reaction by-products greatly affected the adhesion. However, dispersions of these adhesive compositions have low viscosities and poor roll coat suitability. On the other hand, in the adhesive composition of the present invention, both the adhesive strength in the state and the adhesive strength during processing showed adhesive strength leading to film breakage, even though the reaction product was not washed.
The roll coatability was also good.

Further, the adhesive compositions of Comparative Examples 5 and 6 were obtained only at a low level of adhesiveness because the use ratios of maleic anhydride and styrene were not substantially equimolar.

Claims (4)

[Claims] 1. A graft resin obtained by graft-modifying a polyolefin resin dissolved in an organic solvent in the presence of a radical generator, using substantially equimolar amounts of maleic anhydride or maleic acid and a styrene monomer. An adhesive composition obtained by precipitating fine particles of the modified resin from the modified resin solution. 2. A method for producing the adhesive composition according to claim 1. 3. The adhesive composition according to claim 1, further comprising a soluble resin. 4. The soluble resin is an epoxy resin.
The adhesive composition according to the item.