JPS5915157B2 - Adhesive composition for composite laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive composition for composite laminates having excellent hot water resistance and chemical resistance.

For details, see various plastic films, aluminum foils,
The present invention relates to an adhesive composition that provides excellent adhesion, hot water resistance, and chemical resistance when laminating paper and the like to produce a composite film.

In recent years, organic substrates such as zero-film, low-density, medium-density, and high-density polyethylene films, unstretched and stretched polypropylene films, unstretched and stretched nylon 6, 6.6 nylon films, polyethylene terephthalate films, and aluminum foils have been developed. Multilayer composite films, which are laminated in layers or three or more layers using a solvent solution type or solvent-free adhesive (dry lamination method), are particularly popular as materials for food packaging and medical packaging.

After the composite dry laminate film is made into a bag, it is filled with contents and subjected to retort sterilization or pole sterilization while pressurized in high-temperature steam.

The above-mentioned retort or boilable pouch is made by laminating a heat-sealable resin layer such as polyethylene or polypropylene and a heat-resistant resin layer such as polyethylene terephthalate film or 6-nylon film, with an aluminum foil layer provided in the middle if necessary. However, this laminated film is formed into a bag shape with the heat-sealable resin layer on the inner surface, and the periphery is heat-sealed for normal use.

Most adhesives for dry lamination use polyurethane resins due to their excellent performance.
During the retort sterilization process at ~135°C for about 5 to 40 minutes or the pole sterilization process at 80 to 100°C for about 5 to 60 minutes, the adhesive layer may deteriorate due to heat, or the filled contents may be contaminated with food or spices. , cosmetics, or penetrating chemicals, these contents penetrate the inner film and reach the adhesive layer, corrode the adhesive layer, reduce the adhesive strength, and often cause the inner and outer layers to bond. There is a tendency for delamination to occur at the adhesive surface or the adhesive surface between the inner layer and the intermediate layer at °C.

As a result of various studies aimed at improving these drawbacks, the present inventors have discovered an adhesive composition having excellent adhesion, pole resistance, retort resistance, and chemical resistance, and have arrived at the present invention. .

That is, the present invention provides a polyurethane having free NCO groups in its molecular chain (hereinafter referred to as polyurethane (4)) and a silane coupling agent having active hydrogen atoms in its molecular chain (hereinafter referred to as silane coupling agent (B)). The present invention relates to an adhesive composition for composite laminates containing the following.

As the polyurethane (4), one-component polyurethanes having free NCO groups in the molecular chain that are commonly used for composite laminating adhesives can be used, but polyether polyols, polyester polyols, and polyester ethers can be used. 1 selected from the group consisting of polyols
species or two or more polyols and polyisocyanates, and if necessary, compounds having active hydrogen atoms other than those listed above (
For example, those obtained by reacting with low molecular weight polyols can be suitably used.

Polyether polyols used herein include linear or branched polyalkylene polyols such as polyethylene glycol, polypropylene glycol, glycerin or ethylene oxide or propylene oxide adducts of trimethylolpropane. As the polyester polyol, a linear or branched polyester having an 0H group in the molecular chain obtained by reacting a polybasic acid with a low-molecular polyol can be used, and examples of the polybasic acid include adipic acid, azelaic acid, and dodecanedioic acid. , dimer acid, isophthalic acid, phthalic anhydride, terephthalic acid,
Dibasic acids or their esters such as dimethyl terephthalate, itaconic acid, fumaric acid, maleic anhydride, and hexahydrophthalic anhydride; tribasic acids such as trimellitic anhydride; and the like.

In addition, examples of low-molecular polyols include ethylene glycol, diethylene glycol, butylene glycol, 1,6 hexanediol, neopentyl glycol,
Diols such as hydrogenated bisphenol A; glycerin;
Triols such as trimethylolpropane; and polyols having four or more functionalities such as pentaerythritol and sorbitol. When producing this polyester polyol, tetraalkyl titanates, antimony oxide, zinc acetate, etc. may be used as commonly used esterification reaction catalysts. The polyester ether polyol includes a linear or branched polyester having an 0H group in the molecular chain obtained by esterifying the polybasic acid and the polyether polyol, or a mixture of the polyether polyol and the low molecular weight polyol, and a linear or branched polyester having an 0H group at the end. The diesterization reaction in which the polyether obtained by addition-reacting alkylene oxide (e.g. ethylene oxide, propylene oxide, etc.) to a polyester having a carboxyl group and/or hydroxyl group is usually 180 to 2
The reaction may be carried out at a temperature of 50° C. while discharging the produced water out of the reaction system, and if the reaction is carried out under an inert gas atmosphere, a relatively light-colored polyester can be obtained.

The polyether polyol, polyester polyol and polyester ether polyol used in the present invention preferably have an average molecular weight of about 200 to 4,000, particularly preferably about 400 to 2,000.

Examples of organic polyisocyanate compounds include hexamethylene diisocyanate, O-, m- or P-phenylene diisocyanate, 2.4- or 2.6-
Tolylene diisocyanate, aromatic ring hydrogenated 2
・4- or 2.6-tolylene diisocyanate, diphenylmethane 4.4/-diisocyanate, 3.37-
Dimethyl 4,4'-biphenylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate,
Examples include isoborone diisocyanate, ω·ω7-diisocyanate-1,4-dimethylbenzene, and ω·ω7-diisocyanate-1,3-dimethylbenzene, and these can be used alone or in combination.

Furthermore, examples of the low-molecular polyol used as necessary in the production of the polyurethane material include the low-molecular polyols mentioned above as raw materials for the polyester polyol.

In addition, amino alcohols such as ethanolamine and propanolamine, amino compounds such as ethylenediamine and n-butylamine, water, and the like may be used in the production of polyurethane. The urethane-forming reaction for producing polyurethane particles may be carried out at a reaction temperature of usually 50 to 100° C. in the presence or absence of an organic solvent inert to isocyanate groups.

In addition, when carrying out the urethanization reaction, if desired, as a catalyst, for example, dibutyltin dilaurate, stanas-2, etc.
-Ethylhexoate iron-acetylacetonate, triethylenediamine, N-methylmorpholine, etc. may be added in an amount of 0.005 to 0.2% by weight based on the solid content of the resin. The polyurethane (A) thus produced preferably has an average molecular weight of 500 to 50,000 and a molecular weight of 0.5
Those with ~10% by weight of free NCO groups are suitable;
More preferably an average molecular weight of 1000 to 20000 and 2
Those with ~8% by weight of free NCO groups are suitable.

The silane coupling agent 13) used in the present invention has the general formula X-Si(0R)3 (wherein, X is an organic group having at least one active hydrogen atom, and R is a lower alkyl group). .

) are generally preferred. In particular, the organic group represented by X in the above formula is, for example, -C3H6NH2
, C3H6NHC2H4NHCH2CH-CH2, C3
Preferably, it is H6NHC2H4NHCH2COOH, and the lower alkyl group represented by R is a methyl group or an ethyl group. Specific examples of these silane coupling agents (8) include γ-aminopropyltriethoxysilane, N-β(aminoethyl)γaminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and β-mercaptopropyltrimethoxysilane. Ethoxysilane, (CH
3O)3SiC3H6NHC2H4NHCH2-CH=
CH2, (CH3O)3SiC3H6NHC2H4NH
CH2C00H is mentioned.

These silane coupling agents (B) are polyurethane (
A) may be contained in a chemically bonded state,
Further, they may be contained in a simply mixed state without chemically bonding.

Therefore, the silane coupling agent (8) may be added to the reaction system at the beginning or in the middle of the urethanization reaction for producing polyurethane (A), or may be added after the reaction is completed. The content ratio of the silane coupling agent (8) to the polyurethane material is 0.05 to 20% by weight, preferably 0.1 to 10% by weight.

If less than 0.05% by weight is used, the above-mentioned modifying effect will hardly be observed, and if more than 20% is used, the price of the silane coupling agent (8) is high, making it economically disadvantageous.

The silane coupling agent (8) serves to increase the adhesive strength between plastic film and metal foil, and between plastic film and plastic film, as well as to improve the resistance of the laminated composite film to the filling contents during pole or retort processing. The adhesive composition of the present invention may be in the form of either a solvent type or a solvent-free type.
・For lamination, use a commonly used method, such as applying an organic solvent solution type adhesive to the film surface using a dry laminator equipped with a dryer, volatilizing the solvent, and then laminating the adhesive surfaces. method, or a method in which the composition is applied as a solvent-free adhesive to the film surface at room temperature or under heating using a solvent-free laminator, the adhesive surfaces are laminated, and then the composition is cured at room temperature or under heating, etc. will be adopted. As is clear from the examples described later, the adhesive composition of the present invention has extremely excellent adhesive strength and hot water resistance between metal foil such as aluminum foil and plastic film such as polypropylene, polyethylene, nylon, and polyethylene terephthalate. Therefore, it is possible to manufacture an excellent food packaging material in which the metal foil and plastic film do not peel off even during retort or pole sterilization treatment.

The present invention will be specifically explained below with reference to Examples.

All "%" in Examples means "% by weight". Example (1) In a reaction vessel, 90 t of polypropylene glycol 25007 having an average molecular weight of 2000 and 625 t of diphenylmethane-4,4'-diisocyanate (MDI) were added.
The reaction was carried out at .degree. C. for 6 hours to obtain an NCO group-containing polyurethane.

NC of this polyurethane (hereinafter referred to as polyurethane I)
The O group content is 3.5% and its average molecular weight is 250
It was 0. ). ) 1500 t of polypropylene glycol with an average molecular weight of 1500 and tolylene diisocyanate (2.4-/2.6 monoisomeric weight ratio - 80/2
0) 348t was reacted at 90°C for 7 hours to obtain an NCO group-containing polyurethane.

NCO of this polyurethane (hereinafter referred to as polyurethane)
The group content is 4.3% and its average molecular weight is 1850
It was hot.

S) Polypropylene glycol 600y with an average molecular weight of 1000, polypropylene glycol 1407 with an average molecular weight of 700, 1,4-butanediol 36t. ．． After reacting a mixture of MDI4507, ethyl acetate 12397, and 0.27 stannous 2-ethylhexoate as a catalyst at 60°C for 4 hours, 13.47% of trimethylolpropane was gradually added, and the mixture was reacted for 2 hours to produce NC.
An ethyl acetate solution of O group-containing polyurethane was obtained.

This solution (hereinafter referred to as polyurethane solution) has a solid content of 5
0%, the NCO group content was 1.5%, and the average molecular weight of the solid polyurethane was 3,100. 1) Polyester consisting of adipic acid, isophthalic acid, and ethylene glycol (molecular weight: 9001 adipic acid/isophthalic acid/ethylene glycol - 2/2/5 (molar ratio)) 900
7, and MDI5OOt were reacted at 90°C for 6 hours and NC
An O group-containing polyurethane was obtained.

NCO of this polyurethane (hereinafter referred to as polyurethane)
The group content is 5.8% and its average molecular weight is 1400
It was hot. The silane coupling agents shown in Table 1 were added to each of the thus obtained polyurethane 11 and support polyurethane to prepare adhesive compositions 1 to 6 shown in the table.

Composite films were prepared using each of the adhesive compositions in Table 1 in the manner described below. and chemical resistance tests were conducted.

For comparison, polyurethane 11 containing no silane coupling agent and adhesive composition 7 containing polyurethane solution
, 8, 9, and 10, similar tests were conducted. The test method is as follows. The results are listed in Table 2. Preparation of three-layer composite film Composite film (a): Polyethylene terephthalate film (thickness 12μ)/aluminum foil (
Thickness 15μ)/Unstretched polypropylene film (Thickness 5
0μ) Composite film (b): polyethylene terephthalate film (thickness 12μ)/aluminum foil (thickness 15μ)
.mu.)/Low density polyethylene film (thickness: 50 .mu.m) The above two types of composite films were prepared by the method described below.

That is, among the adhesive compositions listed in Table 1, ? 1, 2,
3, 5, 6, 7, 8, and 10 are heated to 80 to 100°C, and 4 and 9 are heated to 2F/2F on a polyethylene terephthalate film at room temperature using a laminator.
The coating was applied in an amount equal to that of Idry, and after evaporating any solvent that contained it, the coated surface was laminated to the surface of an aluminum foil. Then, the adhesive composition was applied to the other side of the aluminum foil of the composite film in the same manner, and the adhesive composition containing the solvent was volatilized, and the applied side was laminated with an unstretched polypropylene film or a low-density polyethylene film.
Thereafter, these bonded films were kept at 40° C. for 3 days to cure the adhesive composition. Adhesion test Composite films (a) and (5) prepared as above
) A test piece with a size of 300 mm x 15 dragons was taken from the sample.

Using these test pieces, adhesive strength was measured using an Instron type tensile tester using T-peel at a peel rate of 300 mm/min. The measured value was the average value of five test pieces of the adhesive strength (7/1511 m) between aluminum foil and unstretched polypropylene film or low density polyethylene.

Retort resistance and pole resistance test using each of composite films (a) and (5).
? ×14? Create a bag with the size of and put the composite film (a)
The bags made of the composite film (b) were subjected to a retort resistance test, and the bags made of the composite film (b) were subjected to a pole resistance test.

As for the contents, water/salad oil = 10 in the retort resistance test.
A bag was filled with a mixed solution of /1 (weight ratio) and water in the pole resistance test. The retort resistance test for this bag is 12
The pole resistance test was conducted at 0° C. for 30 minutes under a pressure of 1.5 kg/Cd, and at 98° C. for 1 hour.

After this, will it be durable? (In the tort test, the adhesive strength and peeling state between aluminum foil and polypropylene film were investigated, and in the pole resistance test, the adhesive strength and peeling state between aluminum foil and low-density polyethylene were investigated. Five bags were each tested.

The results listed in Table 2 are the average values. Chemical resistance test using composite film (5) 12c:m x 14C11
A bag with a size of .

The test was conducted on 5 bags each.

The results listed in Table 3 are the average values. The above test showed that adhesive compositions 1 to 6 of the present invention had better retort resistance of composite films than adhesive compositions 7 to 10 of comparative examples.
It is clear from Tables 2 and 3 that it has excellent pole resistance or chemical resistance.

Claims (1)

[Scope of Claims] 1. In a composite laminating adhesive used to produce a composite film by laminating a plastic film and a plastic film or a plastic film and a metal foil, a polyurethane having a free NCO group in its molecular chain has a molecular An adhesive composition for composite laminates, comprising a silane coupling agent having an active hydrogen atom in the chain. 2 Polyurethane having free NCO groups in its molecular chain,
The adhesive composition for composite laminates according to claim 1, which is a reaction product of one or more selected from the group consisting of polyether polyol, polyester polyol, and polyester ether polyol and polyisocyanate. 3 Polyurethane having free NCO groups in the molecular chain is 5
The adhesive composition for composite laminates according to claim 2, having an average molecular weight of 00 to 50,000 and a free NCO group of 0.5 to 10% by weight. 4 A silane coupling agent having an active hydrogen atom in the molecular chain has the general formula X-Si(OR)_3, where X represents an organic group having at least one active hydrogen atom, and R represents a lower alkyl group. represent. Claims 1 and 2 are compounds represented by
The adhesive composition for composite laminate according to item 1 or 3. 5 The organic group X of the silane coupling agent having an active hydrogen atom in the molecular chain has the formula -C_3H_6NH_2, -C_
3H_6NHC_2H_4NH_2, -C_3H_6S
H, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -C_3H_
6NHC_2H_4NHCH_2CH=CH_2 and -
Claim 4 which is an organic group selected from the group consisting of C_3H_6NHC_2H_4NHCH_2COOH
1. Adhesive composition for composite laminate as described in . 6. Claims 1 and 2, wherein the content of the silane coupling agent having an active hydrogen atom in the molecular chain is 0.05 to 20% by weight of the polyurethane having a free NCO group in the molecular chain. , the adhesive composition for composite laminates according to item 3, item 4, or item 5. 7. The adhesive composition for composite laminate according to claim 6, wherein the adhesive composition contains an organic solvent. 8. The adhesive composition for composite laminate according to claim 6, wherein the adhesive composition does not contain an organic solvent.