JPS60139772A - Hot-melt adhesive - Google Patents

Abstract

PURPOSE:To provide the titled adhesive suitable for use in bonding an olefin/ vinyl alcohol copolymer to a polyester, comprising a polymer contg. an ester repeating unit, an oxirane ring-contg. compd. and an acid group-contg. compd. in a specified concn. CONSTITUTION:A compsn. contains a polymer (A) contg. an ester repeating unit, an oxirane ring-contg. compd. (B) and an acid or anhydride group-contg. compd. (C) in such a quantity that the compd. (B) is used in a quantity giving an oxirane oxygen concn. of 0.01-100mmol/100g of compsn. and the compd. (C) is used in a quantity giving a carboxyl group concn. of 0.1-300mmol/100g of compsn. The polymer (A) should have an MW capable of forming a film and a m.p. or softening point of 40-270 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot melt adhesive, and more particularly to a hot melt adhesive having a novel composition and suitable for adhering an olefin-vinyl alcohol copolymer to polyethylene terephthalate, etc. related to adhesives.

Olefin-vinyl alcohol copolymers, especially saponified ethylene-vinyl acetate copolymers, are among the various thermoplastic resins that have the best barrier properties (permeation resistance) against various gases such as oxygen and aroma components. However, although this resin exhibits excellent gas barrier properties under low humidity conditions, it has the disadvantage that gas permeability increases significantly under high humidity conditions.

In order to improve this drawback, a moisture-resistant thermoplastic resin such as polyolefin is laminated on the olefin-vinyl alcohol copolymer layer, and the laminate is widely used as a cup, bottle, tube, or film container. Polyester and polycarbo*-todoethylene-vinyl alcohol-y are also used in stretched blow bottles.
Both! ! However, since there is almost no thermal adhesion between the olefin-vinyl alcohol copolymer and the olefin resin, polyester, or polycarbonate, lamination of both resins is difficult. It is left to the use of adhesive.

This adhesive exhibits excellent adhesion to both of the resins mentioned above, as well as ease of lamination bonding and simultaneous extrusion of laminated products.
From the standpoint of manufacturing, it is desirable that the material be thermoplastic, capable of thermal bonding, and capable of thermoforming. As an adhesive that satisfies such requirements, an acid-modified olefin resin or a resin that is graft-modified with an ethylenically unsaturated carboxylic acid or its anhydride is used for the combination of an ethylene-vinyl alcohol copolymer and a polyolefin. In the industry, hemp is the only adhesive whose composition is known and which is used industrially.
Also related to the desire to produce thinner containers by stretch forming or drawing the adhesive laminate structures mentioned above, the advent of higher performance hot melt adhesives. is lost.

In particular, when manufacturing bottles with excellent transparency, rigidity, and impact resistance by biaxial stretching blowing of polyester such as polyethylene terephthalate or polycarbonate, laminating this with ethylene-vinyl alcohol copolymer itself is difficult. Although many proposals have been made, no definitive hot melt adhesive has yet been found to firmly bond ethylene-vinyl alcohol copolymer and polyester or polycarbonate.

Therefore, the object of the present invention is to produce an olefin/vinyl alcohol copolymer, polyester, polycarbonate,
Shows strong adhesion to other thermoplastic resins such as polyamide,
Moreover, it is an object of the present invention to provide a single adhesive that can be thermoformed and thermally bonded.

According to the present invention, the composition comprises at least one polymer having an ester repeating unit, an oxirane ring-containing compound, and an acid or acid anhydride group-containing organic compound,
The oxirane ring-containing compound is at a concentration sufficient to provide an oxirane oxygen concentration of 0.01 to 100 mmol/'L/100g composition, and the nucleic acid or acid anhydride group-containing organic compound is at a concentration of 0.1 to 600 mmol/' A hot melt adhesive is provided, each of which is present in a concentration sufficient to provide a carboxyl group concentration of a 101 composition.

The present invention provides at least one polymer having an ester repeating unit, an oxirane ring-containing compound, an acid to acid anhydride group-containing organic compound, an oxirane acid system concentration based on the oxirane ring-containing compound, and an acid to □ υ This is based on the new finding that the adhesive strength is significantly improved when the components are blended so that each of them is constant.

Conventionally, polyester-based hot melt adhesives made of resins having ester repeating units have been known per se, and it is known that these hot melt adhesives exhibit excellent adhesion to polyethylene terephthalate films, metals, etc. It is being

However, in a structure in which this polyester-based hot melt adhesive is used to bond polyethylene terephthalate and olefin-vinyl alcohol copolymer, the mechanically weakest part C is the adhesive layer and olefin-vinyl alcohol copolymer. Even if the vapor deposition interface with the copolymer layer exhibits a certain degree of adhesion, for example, at the stage of bottle molding preforms and pipes, or plug-assist molding sheets, these cannot be processed by stretch blow molding, plug-assist molding, etc. When subjected to a stretch-molding operation, it is observed that it decreases to almost the order of zero at the stage after the molding or at the stage with time. In contrast, according to the present invention,
When a polymer having ester repeating units is blended with an oxirane ring-containing compound such as epoxidized soybean oil and an acid or acid anhydride compound, the peel strength at the thermal bonding interface with EVOH is within the range where peeling is impossible. , generally 2-4/
This improves the width to a range of 1.5 m or more, and the unexpected effects of the present invention become clear.

This improvement in adhesive strength can be achieved by using thermoplastic polyesters such as polyethylene terephthalate, polycarbonates,
Further, the same applies to polyamides. □ According to the present invention, remarkable adhesion can be achieved by using a composition containing a polymer having ester repeating units, an oxirane ring-containing compound, and an acid or acid anhydride compound for adhesion to a resin film such as EVOE. In addition to providing increased strength, the composition has the significant advantage that it can be thermoformed like conventional thermoplastic polyesters and is also easily heat bonded.

In the present invention, an olefin-vinyl alcohol copolymer (EV
Although the reason why the adhesive strength with resin films such as OH) is significantly improved has not yet been fully elucidated, the present inventors speculate that the reason is as follows. in general,
It is known that epoxy resins firmly adhere to the surface of the other party that comes into contact with them during curing, but the composition of the present invention also has acid groups and acid anhydride groups in acids and acid anhydrides that can be used during thermal bonding. Naturally, it is expected that a reaction will occur between the oxirane ring (epoxy group) in the oxirane ring compound and the oxirane ring (epoxy group) in the oxirane ring compound, but it is recognized that a strong adhesion is formed between the resin and the resin such as KEVOH during this reaction. .

In addition, the presence of an oxy-2 compound between the acid or acid anhydride group in the acid or acid anhydride and the polar group in the resin, such as the hydroxyl group in EVOII, increases the chemistry of both phase lipid layers. The reason for this is thought to be that the bonding occurs more closely and reliably.

In addition to the chemical bonding that occurs at the interface between the two resin layers, one factor is also believed to be that in the case of thermal bonding, the resins are mixed well at the adjacent interface between the two resins. Seem. That is, for example, many oxirane ring compounds such as epoxidized soybean oil also act as plasticizers,
It is presumed that the oxirane ring compound blended into the formulation improves the wettability between both resin layers and improves the mixing of both resins at the adhesive interface due to its plasticizer action. Furthermore, it is recognized that such action as a plasticizer significantly improves the thermoformability of the adhesive layer, such as extrusion characteristics and coating workability, and also improves thermal bonding workability.

Furthermore, many of the oxirane ring compounds are known to impart a thermal stabilizing effect to the resins in which they are blended. Even when the adhesive of the present invention is blended with relatively poor thermal stability, the stability during thermoforming and heat bonding is significantly improved by blending the oxirane ring compound.

In the present invention, a thermoplastic polyester or a copolymer polyester derived from a dibasic acid component and a dihydroxy component is used as the polymer having ester repeating units.

Suitable examples of such thermoplastic polyesters include, but are not limited to:

Or 1 (+'0-R1+rL, 0-R, C+-...
...In the formula (2), +('-R1+ is a carbon number of 2 to 6
0 oxyalkylene group, and a polymer thereof, R3 is an alkylene group or arylene group having 2 to 24 carbon atoms, and a polyester comprising a repeating unit represented by the following.

Here, dibasic acid components include terephthalic acid, isophthalic acid, adipic acid, cepatic acid, maleic acid, simaric acid, etc., and glycol components include ethylene glycol, tetramethylene glycol, propylene glycol, neopentyl glycol, diethylene glycol, and triethylene glycol. , polyethylene glycol, and polyalkylene glycols made of these polymers, homopolymers each consisting of one component, or copolymer polyesters containing a plurality of one or both components, such as polyethylene terephthalate/ Adipate, polyethylene inphthalate/separate,
Polyethylene terephthalate/isophthalate, polytetramethylene isophthalate, polyethylene terephthalate/isophthalate; polytetramethylene terephthalate, polyethylene/tetramethylene terephthalate,
Polyethylene/oxypenshade, polyethylene terephthalate/polyoxyethylene terephthalate, block copolymers, etc.

Here, for the purpose of modifying the film properties, some of these materials may be blended, or a portion of other resins such as polyolefin resins such as polyethylene, polypropylene, ionomer, ethylene vinyl acetate copolymer, modified polypropylene, etc. may be blended. Sometimes it is used as

The polyester used in the present invention should have a molecular weight sufficient to form a film in terms of physical properties, and its melting point to softening point is preferably in the range of 40 to 270°C.

On the other hand, as the oxirane compound, any compound having at least one oxirane ring in the molecule can be used. The oxirane compound may be in any liquid, solid or semi-solid form, as long as it can be blended with the acid-modified olefin resin.

Suitable examples of oxirane ring-containing compounds include, but are not limited to, the following:

(1) Epoxidized soybean oil epoxidized castor oil, epoxidized linseed oil, epoxidized flower oil, Epoxidized glycerides such as.

(2) Epoxidized fatty acid esters such as epoxidized linseed oil fatty acid butyl, epoxidized octyl oleate, 1so-octyl, 2-ethylhexyl, and the like.

An epoxy hexahydrophthalate ester represented by the following, wherein R is a higher alkyl group such as a 2-ethylhexyl group or an isododecyl group.

(4) 3-(2-xenoxy)-1,2-epoxypropane, styrene oxide, vinylcyclohexene oxide, glycidyl acrylate, phthalic acid glycidyl ester, epoxidized polybutadiene, phenyl glycidyl ether, polyethylene glycol bisepoxide, bisphenol A Other oxy2F-containing compounds such as bisepoxides.

In the present invention, among the above-mentioned oxirane ring-containing compounds, the epoxidized carboxylic acid esters (1) to (3) are particularly preferred.

In addition, examples of organic compounds containing acid or acid anhydride groups include acid anhydrides conventionally used as curing agents for epoxy resins, ethylenically unsaturated carboxylic acids and their anhydrides, and resins modified with these. It can be used in many ways.

Suitable examples of acid anhydrides are phthalic anhydride, dodecylsuccinic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, benzophenonetetracarginic anhydride, chlorenditic anhydride, methylcyclopentadiene anhydride. Maleic acid adducts, etc.

Examples of ethylenically unsaturated acids or acid anhydrides include acrylic acid, meta-winteric acid, crotonic acid, maleic acid,
-r acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, etc. Among these, maleic anhydride is particularly preferred. .

Instead of directly blending the above-mentioned acids and acid salts, it is also possible to use graft-modified acids with ethylenically unsaturated acids or acid anhydrides. In this case, the backbone polymer of the graft copolymer is low density, medium density or high density polyethylene, tactical polypropylene, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer. 1 copolymer, ethylene-
Vinyl acetate copolymer, ionically crosslinked olefin copolymer (
ionomer) or a blend of two or more thereof, and the polyesters exemplified above can be used as the backbone polymer.

The adhesive composition of the present invention contains carboxyl groups based on acid or acid anhydride in a concentration of 0.1 to 300 mmol, particularly oxirane in a concentration of 1 to 200 mmol, per 100 g of the composition. It is also important to contain oxirane oxygen based on ring-containing compounds in a concentration of 0.01 to 100 mmol, in particular 0.1 to 50 mmol.

Note that an acid anhydride is obtained by dehydrating two acids (carboxyl groups), and therefore, one acid anhydride corresponds to two carboxyl groups.

That is, when the carboxyl group concentration or oxirane oxygen concentration is lower than the above-mentioned range, the adhesive strength to the resin layer such as EVOII becomes considerably inferior to that of the present invention. On the other hand, if the carboxyl group concentration or oxirane oxygen concentration is lower than the above range, thermoformability and thermal adhesion tend to decrease, and in particular, the adhesive layer itself has a unique odor and color. It will be done.

In addition, in the resin composition of the present invention, there is a tendency for a reaction to occur between the oxirane ring and the acid or acid anhydride group during thermal bonding, so the carbonyl group concentration and oxirane oxygen concentration mentioned above are based on the time of compounding. means concentration.

The combination of an acid or acid anhydride and an oxirane ring-containing compound into a polymer having ester repeating units can be easily carried out by dry or wet blending of the two, or by kneading under heat and pelletizing if necessary. be exposed. However, from the standpoint of preventing interaction between the two before adhesion as much as possible, first the oxirane ring-containing compound is kneaded with a polymer having ester repeating units and pelletized, and this pellet and the polymer having ester repeating units are mixed together. It is preferable to tri-blend the mixture and the mixed pellets of acid or acid anhydride, and melt this tri-blend product for thermal bonding at the time of use.

The adhesive of the present invention can be coextruded through a multilayer die between the EVOII layer and a moisture resistant thermoplastic such as an olefin resin, polyester, polycarbonate, etc.
It can be used for adhesion by intervening in the form of a melt. Furthermore, the composition can be used in the form of a film, in the form of a powder, as well as in the form of a suspension, emulsion or solution, for bonding EVOH with other moisture-resistant resins.

The film can be formed by means known per se, such as the T-die method. For example, powder formation can be done by mixing wire pellets,
Either by grinding at a low temperature such as under cooling with liquid nitrogen, or by dissolving this composition in an organic solvent such as decalin or hot xylene,
It is formed by pouring it into such a non-solvent and depositing it in the form of fine particles.

The adhesive of the present invention is not only useful for lamination bonding between an EVOH layer and a moisture-resistant resin layer such as polyolefin, polyester, or polycarbonate, but also for lamination bonding of any combination of resin layers, or for bonding these resin layers with aluminum. It can also be used for adhesion with metal foils such as foils.

The invention is illustrated by the following example.

Example Extruder for inner and outer layers with a built-in full-flight screw with a diameter of 65φ and an effective length of 1.430m+, a diameter of 50φ
, an extruder for the middle layer and an extruder for the adhesive layer with a built-in full-flight screw with an effective length of 1.100 mm, and a flat die for 5 parts, the inner and outer layers are made of polyethylene terephthalate, and the middle layer contains vinyl alcohol. an ethylene vinyl alcohol copolymer in an amount of 70 molt and an adhesive layer,
A copolyester of 95 parts of terephthalic acid, 5 parts of iso7-thalic acid and ethylene glycol, and 2 parts of maleic anhydride.
A composition with a carbonyl group concentration of 50 mmol/101 mixed with 5,000 ppm and 10,000 p of epoxidized linseed oil with an oxirane oxygen content of 9- to the copolyester.
Inner layer: 6 kinds of 5-layer sheets with an average thickness of 800 μm, each of which is a composition in which PM is mixed in the proportions shown in Table 1 below:
The thickness of adhesive layer: intermediate layer: adhesive layer: outer layer is 10:2:1:
It was molded so that the ratio was 2:10.

After heating this laminated sheet to the orientation temperature (112°C),
A cup-shaped container having an internal volume of 600 cc was stretch-molded by plug-assisted pressure forming.

Table 1 Using the side wall of the obtained cup-shaped container as a test piece, the adhesive strength with the ethylene vinyl alcohol copolymer layer was measured by T-peel peeling. The results are shown in Table 2. Note that the interface between the polyethylene terephthalate and the adhesive layer could not be peeled off.

Table 2

Claims (1)

[Claims] (1) Consists of a composition containing at least one polymer having an ester repeating unit, an oxirane ring-containing compound, and an acid or acid anhydride group-containing organic compound, the oxirane ring-containing compound having 0 .01 to 100 mmol/10
01/The nucleic acid or acid anhydride group-containing organic compound is present at a concentration sufficient to provide the oxirane oxygen concentration of the composition, and the nucleic acid or acid anhydride group-containing organic compound is present at a concentration of 0.1 to 600 mmol/100Ji [each is present at a concentration sufficient to provide the carboxyl group concentration of the composition] A hot melt adhesive with unique characteristics.・