JPS5971378A - Heat-sensitive film adhesive - Google Patents

Abstract

PURPOSE:The titled adhesive, obtained by graft modifying a specific polyamide orligomer in a specific amount onto the side chain of a backbone ionomer prepared by ionizing an ethylene-alpha,beta-unsaturated carboxylic acid copolymer, and having both low-temperature and heat-resistant adhesive properties. CONSTITUTION:An adhesive obtained by graft modifying (B) 3-20wt% polyoligomer, preferably polycaprolactam, polylaurolactam or copolymeric polylactam, having 4-35 polymerization degree onto the side chain of (A) 80- 97wt% backone ionomer prepared by ionizing 5-50% ethylene alpha,beta-unsaturated carboxylic acid copolymer, e.g. ethylene-methacrylic acid copolymer, with zinc ions. EFFECT:Economical and advantageous film moldability. USE:Building materials, wood working material, automotive parts, electric appliances and parts for aircraft.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved heat-sensitive ethylene copolymer film adhesive that has a well-balanced combination of melt adhesion at low humidity and heat-resistant adhesion. In a copolymer with a carboxylic acid, a portion of the acid in the copolymer is neutralized with metal ions, and a polyamide oligomer is catalytically reacted with an ethylene copolymer (hereinafter referred to as an ionomer) to form the ionomer. This invention relates to a film adhesive formed by introducing a polyamide oligomer into the side chain.

In general, the properties required for resins for heat-sensitive film adhesives include economical film formability, as well as lower temperature in terms of adhesive work efficiency and damage caused by heat deformation and deterioration during bonding of base materials. There has been a strong demand for properties that allow for melt bonding (low-temperature adhesion) and at the same time maintain adhesive strength during thermal bonding and when the bonded structure is exposed to high temperatures (heat-resistant adhesion).

However, these properties are contradictory, and it has been difficult to obtain a resin film that has a well-balanced combination of properties such as film formability, low-temperature adhesion, and heat-resistant adhesion. For example, polyolefin resins, especially ethylene copolymer systems, such as ethylene-vinyl acetate copolymer, :xtiL/>-7 acrylic acid ester copolymer,
Film adhesives such as ionomers can be bonded at relatively low temperatures of around 100°C and have excellent low-temperature adhesive properties, but these copolymer films have relatively low melting points and low melt viscosity above the melting point. It has poor heat-resistant adhesion. On the other hand, W IJ with high melting point such as polyamide-based and polyester-based resins
Fl? Although the film is known as a heat-resistant film, the temperature dependence of the melt viscosity is large above the melting point, and the melt viscosity rapidly decreases, causing problems in maintaining adhesive strength during thermal bonding, and the strength of the melt film is low. It has the disadvantage that it cannot be formed into a film using the in-7 ratio method, and is therefore uneconomical. Furthermore, polyester-based adhesives have poor low-temperature adhesion.

The present inventors took advantage of the economically advantageous properties of ethylene copolymer-based heat-sensitive film adhesives, such as film formability and low-temperature adhesion, while improving the heat-resistant adhesion, which is a drawback of these adhesives. As a result of intensive studies to obtain a heat-sensitive film adhesive that has a good balance of the properties required for the heat-sensitive film adhesive, we identified an ionomer, namely an ethylene-α,β-unsaturated carboxylic acid copolymer. The present inventors discovered that a graft modified product obtained by catalytically reacting 3 to less than 20% by weight of a polyamide oligomer with an ionomer 5 to 50% ionized by zinc ions achieved the above object, leading to the completion of the present invention. . That is, the present invention relates to an ethylene copolymer-based heat-sensitive film adhesive that has a well-balanced combination of economical film formability, low-temperature adhesion, and heat-resistant adhesion.

In addition, the low-temperature adhesion and heat-resistant adhesion referred to in the present invention are each
The heat sealing temperature and shear bond failure temperature are used as indicators.

Among ethylene copolymers, ionomer has low-temperature adhesive properties,
It has the advantages of adhesion to base materials such as wood and metal, film strength, film formability, and ease of handling because the film does not bunch up easily, but on the other hand, the melting point is relatively low, so the adhesive part has the melting point. If exposed to high temperature conditions above, adhesive strength cannot be maintained and it cannot be used for adhesive applications that are used at high temperatures. It is known that the heat resistance of the ionomer can be improved by grafting a polyamide oligomer onto the ionomer, as measured by a thermal deformation test. (
JP-A-55-2148';').

However, the modified ionomers obtained by these methods can be used as adhesives by adding or grafting 20% by weight or more of polyamide or polyamide oligomer to the ionomer to improve heat resistance. However, compared to the basic ionomer, there are problems such as decreased adhesion to substrates and loss of low-temperature adhesion. Furthermore, no further improvement in heat-resistant adhesion is observed at 20% by weight or more. Furthermore, in order to mold a modified ionomer into a film, it is necessary to mold it at a temperature higher than the melting point of the polyamide or polyamide oligomer in the modified ionomer, and in this case, the melt viscosity of the resin becomes extremely low and the molten resin film becomes unstable during film molding. Film forming using the inflation method is difficult and uneconomical. Needless to say, these drawbacks become more noticeable as the amount of polyamide or polyamide oligomer added increases. This is a serious drawback for film adhesives.

Examples of the ethylene-α,β-unsaturated carboxylic acids that are the base resin of the ionomer used in the present invention include ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethyl/-itaconic acid copolymer, and ethylene-acrylic acid copolymer. Acid-
Examples include methyl methacrylate copolymer, ethylene-methacrylic acid-ethyl acrylate copolymer, and ethylene-methacrylic acid-vinyl acetate copolymer. Furthermore, if necessary, these copolymers may be blended with other thermoplastic resins.

The graft modified product in the present invention can be produced by catalytically kneading the ionomer and the polyamide oligomer at a temperature above the melting point of the base ionomer, preferably from 150 to 250°C. The reaction device may be of any type as long as it melts and kneads the polymer, but a screenie extruder is suitable. In this case, the ionomer is ionized with zinc ions from the viewpoint of reactivity with the polyamide oligomer, and the degree of ionization is 5 to 50% from the viewpoint of improving heat-resistant adhesion and reactivity by graft modification of the polyamide oligomer. Yes, preferably 10 to 40%.

Ionomers ionized with metals other than zinc, such as sulfur, potassium, magnesium, etc., do not have the effect of promoting the reaction when the carboxylic acid in the ionomer and the amino group end of the polyamide oligomer react and bond. Ionomers ionized with are not suitable.

Further, if the degree of ionization is 5% or less, the reaction promoting effect by zinc ions is lost, and if the degree of ionization is 50% or more, no remarkable heat-resistant adhesion improvement effect is exhibited. In general, ionomers with a high degree of ionization have the best heat-resistant adhesion, but when graft-modifying the ionomer with a polyamide oligomer, an ionomer with the above degree of ionization has better heat-resistant adhesion than an ionomer with a high degree of ionization. Provides greater effectiveness and higher heat-resistant adhesion.

This is because the mechanism by which heat-resistant adhesion is improved is that the high melting point polyamide armor is bonded to the main chain of the ionomer, and that the intermolecular and molecular It is presumed that this is because the viscosity of the graft modified product becomes extremely high in a temperature range above the melting point of the ionomer and below the melting point of the polyamide oligomer and under low shear stress due to the synergistic effect of internal interactions. This assumption is based on the fact that blends of ethylene-α, β-unsaturated carboxylic acid copolymers and polyamide oligomers, in which grafting reactions do not proceed easily, or simple blends of ionomers and high-molecular-weight polyamides will hardly improve heat-resistant adhesion. is also supported. This has not been known from conventionally known techniques.

In the present invention, it is particularly important that the amount of polyamide oligomer in the graft modified product is from 6 to less than 20% by weight in order to complete the present invention. In other words, if the amount of grafted polyamide oligomer exceeds 20% by weight, not only will the advantages of the ionomer's adhesive properties and low-temperature adhesive properties be greatly impaired, but also the melt strength of the resin will be low and the molten film will not be stable during film molding, making inflation molding difficult. This is impossible and uneconomical, making it unsuitable for use as a film adhesive.

The first polyamide oligomer used in the present invention has a primary amino group at one end, and an N-carbon group having 1 to 20 carbon atoms at the other end.
- terminated with an alkylamido group. This is to prevent further polymerization of the oligomer due to the temperature during the graft reaction.

The polyamide oligomer uses lactam or ω-aminocarboxylic acid as a monomer and n-alkylamine as an end capping agent. The most preferred polyamide oligomers include polycarbolactam, polylaurolactam, or copolymerized polylactam.

The preferred average degree of polymerization of the oligomer is 4 to 35; if the average degree of polymerization is less than 4, the effect of improving heat-resistant adhesion is small.
If it is larger, the grafting reaction rate will be slow and it will be impractical.

The heat-sensitive film adhesive obtained by the present invention retains the advantages of ionomers, such as low-temperature adhesion and film processability, and is superior to polyamides and polyesters, which have been conventionally used as heat-resistant film adhesives. It exhibits superior heat-resistant adhesive properties, properties that could not be achieved with conventional heat-sensitive film adhesives. The advantage of the properties of these film adhesives is that they can not only withstand use at high temperatures, but also allow the bonded structure to be moved or to apply stress to the bonded area while the bonded area is at a high temperature after thermal bonding. Therefore, when bonding materials with low thermal conductivity such as wood or asbestos, there is no need for cooling time in the bonding cycle, which is advantageous for improving work efficiency.

The heat-sensitive film adhesive of the present invention adheres well to metals, paper, wood, glass, asbestos, various resins, etc., and is useful for applications such as building materials, woodworking, automobile parts, electrical products, and aircraft parts.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but it is not limited thereto in any way.

The physical property values shown in each example were measured by the following method.

(Measurement method) 1) Shear adhesive failure temperature (measured as an index of heat-resistant adhesion) Two soft aluminum plates are glued together using a film adhesive, bonding temperature is 200°C, bonding area is 1.5crI) in a direction perpendicular to one aluminum plate. Apply a load to and suspend it while open. The temperature of the oven is increased from 50° C. at a heating rate of 15° C./hr, and the temperature at which the adhesive portion breaks is measured. Load is 100.9/1.5
i, 500g/l, 5cr! Two types were used.

2) Heat-sealability (measured as an index of low-temperature adhesion) Two adhesive films are sandwiched between seal bars, heated, and thermally bonded under pressure. Determine the minimum temperature at which thermal bonding is possible by measuring bonding temperature and seal strength.

The heat sealing conditions were a pressure of 2 kg/i, a sealing time of 07 seconds, a sealing width of 5 myz, and single-sided heating, and the sealing strength was determined by a 90° peel test.

6) Heat deformation rate (measured as an index of heat resistance) test piece (width 2
Fix one end of a heat-pressed sheet (5 mm long, 100 mm long, 3 tnm thick) to make the test piece horizontal. After being left at a specific temperature for 2 hours, the deflection of the other end is measured and the deformation rate (automatic deformation rate) at that temperature is calculated using the following formula.

(Test piece length: 100 dragons) The contents of the ionomers used in the examples are as follows.

Table 1 *Isobutyl acrylate Example 1 Ionomer-1 pellets and polyamide oligomer (
Polycaprolactam, number average degree of polymerization 22.3, melting point 21
3° Csn-hexylamine to block the terminal carboxyl amine) powder was tri-blended in the proportions shown in Table 2, and then placed in a single-screw extruder (screw diameter 30,
L/D = 152), and was kneaded and extruded to obtain pellets of a graft copolymer of polyamide oligomer to ionomer. The resin temperature in the extruder is approximately 220
℃, the die temperature was about 200° C., the Sufu IJ x-rotation speed was 45 revolutions per minute, and the average residence time of the resin in the extruder was about 3 minutes and 30 seconds. The obtained belet) was transparent.

The pellets were subjected to inflation flake film molding using an extruder having a screen diameter of 30 mm. The resin temperature during film molding is 200-220℃ and the film thickness is 100μ.
It is m. Film molding was easy, and F-rubles such as bubble meltdown, film deformation, and blocking did not occur at all. The resulting film was transparent.

The heat-resistant adhesive properties of these films were measured by shear bond failure temperature, and the heat-resistant adhesive properties were significantly improved compared to the original ionomer. The results are shown in Table 2.

Comparative example 1. Reference Example 1 Table 2 shows the shear bond failure temperatures of the ionomer film of Example 1, polyamide and polyester for thermal bonding as a comparative example and a reference example regarding the heat-resistant adhesive properties of the film.

Table 2 Note 1) Polyamide film; 12 nylon, melting point 108°C, film 4J8D μm2) Polyester film: Copolymerized polyester, melting point 118°C, film thickness 80 μm Example 2 Comparative Example 2 The polyamide oligomer used in Example 1 was used as ionomer 2. 5.1015% by weight of each was grafted according to the method of Example 1. This graft copolymer was processed into a film in the same manner as in Example 1. Film processing was easy and a transparent film was obtained.

As a comparative example, the same ionomer was blended with 5%, 10%, and 15% by weight of a high molecular weight polyamide (Amilan CM-1021, 6 nylon, manufactured by Toshishi ■, melting point 215°C) using an extruder according to the method of Example 1.

This blended resin was processed into a film in the same manner as in Example 1. Film processing was easy, but a translucent film was obtained.

Next, we measured the heat-resistant adhesion of a film of an ionomer grafted with this polyamide oligomer and an ionomer blended with nylon 6 by shear bond failure temperature, and found that the heat-resistant adhesion of the boryamide oligomer-grafted ionomer was significantly improved. On the other hand, no blending of nylon 6 was observed.

The results are shown in Table 6.

Table 3 Film thickness: 1 (30 μm) Example 6 Comparative Example 6 Example 1 7 In the same manner as in Example 1, the polyamide oligomer used in Example 1 was grafted onto the ionomer shown in Table 4. The amount of polyamide oligomer was increased. However, when the amount of oligomer grafting exceeds 20% by weight, the resulting graft copolymer becomes opaque, and the resin pressure in the extruder decreases rapidly, causing the resin strands coming out of the extruder to become filamentous. A phenomenon of dripping from Gui appeared.

When the obtained graft copolymer was formed into a film in the same manner as in Example 1, the oligomer graph) was 20
If the amount of graft copolymer exceeded the weight percentage, bubble meltdown occurred and film formation could not be performed.

Furthermore, when the adhesive strength of this graft copolymer to an aluminum plate was measured, the amount of oligomer grafting was 20! ff
It was found that those with a grafting amount of more than i% had significantly lower adhesive strength than those with a smaller amount of grafting, and were therefore unsuitable as adhesives.

Comparative Example 4 Using the same equipment and under the same conditions as Example 1, 10% by weight of the polyamide oligomer used in Example 1 was added to an ionomer with a high degree of ionization, an ionomer in which the metal ion species is not zinc, and an ethylene/methacrylic acid copolymer. I tried grafting. Although it is unclear whether or not there was a graft reaction, the product was milky white and opaque or translucent.

The product was processed as in Example 1 into a 100 μm thick film. Although film processing was easy,
The film was translucent.

When this film was measured for heat-resistant adhesion and adhesive strength to aluminum, it was found that the degree of improvement in heat-resistant adhesion was very small compared to Example 1, or the adhesive strength was insufficient. It was insufficient as a drug.

The results are listed in Table 5.

Example 4 Comparative Example 5 Regarding the films of polyamide graft ionomer, ionomer, polyamide, and polyester shown in Table 6, low humidity adhesion, heat resistant adhesion, and adhesion strength were evaluated, respectively, by heat seal strength, shear adhesion failure temperature, and the relationship with aluminum plate. It was measured by adhesive strength. The polyamide oligomer of the example had low-temperature adhesion and adhesion strength at the same level and significantly superior #I adhesion resistance compared to conventional heat-sensitive film adhesives. On the other hand, the polyamide oligomer graft ionomer (Comparative Example 5) with a high polyamide oligomer content of 25 folds has good heat-resistant adhesion, but its heat-sealability and adhesive strength are insufficient, making it unsuitable for use as a heat-sensitive film adhesive. It was sufficient.

Example 5 Reference Example The adhesion between the polyamide oligomer graft ionomer film shown in Table 7 and various substrates was measured by shear adhesive strength. Similar measurements were also made for the commercially available heat-sensitive film adhesives shown in Table 6 for comparison. All had adhesive strength sufficient for practical use.

In addition, when bonding with polyamide oligomer graft ionomer, it was possible to remove the bonded object without cooling it after bonding, but with commercially available adhesives, if you move the bonded object without cooling it, the bonded part will move and break. It was taken out after cooling.

The results are shown in Table 7.

Example 6 Comparative Example 6 Polyamide oligomers (polycaprolactam, terminal carboxyl group sealed with n-hexylamine) having different degrees of polymerization shown in Table 8 were added to ionomer 1 at a ratio of 90% by weight of ionomer and 10% by weight of polyamide oligomer. Then, using a Prabender Plastograph, the mixture was kneaded for 10 minutes at 220°C to cause a reaction.

The reactant was molded into a 200 μm thick film by hot pressing, and heat-resistant adhesiveness was measured by shearing adhesive failure temperature. Those with a low average degree of polymerization of the oligomer had a poor degree of improvement in heat-resistant adhesion in practical terms, and those with a high degree of oligomer polymerization had insufficient grafting reaction, resulting in a milky white film and little improvement in heat-resistant adhesion. The average degree of polymerization of the oligomer used was suitably about 4 to 35.

Table 8

Claims (1)

[Claims] A basic ionomer made of 5-50% ionization of ethylene/α,β-unsaturated carboxylic acid copolymer with zinc ions, with an average degree of polymerization of more than 80 weight fIt% and 97 weight% or less, and an average degree of polymerization of 4-35.
Polyamide oligomer having 3% by weight or more, 20% by weight
A heat-sensitive film adhesive obtained by graft-modifying side chains with less than iIC%.