JPS649348B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to hot melt adhesives. More specifically, the present invention relates to a hot melt adhesive that has an excellent balance of various properties. Hot melt adhesives comprising an ethylene-vinyl ester copolymer resin or an ethylene-α,β-unsaturated carboxylic acid ester copolymer resin and a tackifier are conventionally known. Although these hot melt adhesives are widely used in fields such as packaging, bookbinding, and woodworking, they have the drawback of insufficient heat resistance. It is clear that these drawbacks can be overcome by using the above-mentioned ethylene copolymer resins with a low comonomer content, but this will reduce the essential adhesiveness.
These solutions are not possible. JP-A No. 51-125466 discloses that a low degree of polymerization (oligomer) polyamide was graft copolymerized to an ethylene-vinyl acetate-maleic anhydride ternary random copolymer, and the resulting graft copolymer was hydrogenated. Addition of a tackifier such as wood ester gum yields a high-temperature melt adhesive that has a decay temperature (corresponding to the shear failure temperature referred to in the Examples below) for adhesive peeling in an oven. It is described that the properties of the material are considerably improved, that is, the resistance to breakage is large. However, the industrial production of ethylene-vinyl acetate-maleic anhydride ternary random copolymer has problems such as corrosion of production equipment and abnormal reactions caused by maleic anhydride, making it difficult to ensure safety. It is generally accompanied by difficulties. On the other hand, when an ethylene-vinyl acetate copolymer resin is graft-modified with maleic anhydride and a polyamide oligomer is further graft-copolymerized with this, the maleic anhydride graft-modified resin can be produced in two ways using an extruder or the like. It has been discovered that not only can this process be carried out relatively easily through subsequent modification, but also that the final polyamide oligomer graft copolymer resin can be used as a hot melt adhesive with an excellent balance of various properties. Ta. Furthermore, in the present invention, as described above, ethylene-vinyl ester copolymer resin is used as the base polymer of the graft copolymer resin, but ethylene-α,β-unsaturated carboxylic acid ester copolymer resin is also used. Also used in the same way. Therefore, the present invention relates to a hot melt adhesive that is extremely well balanced in various properties including shear failure temperature. It consists of a polyamide oligomer graft copolymer resin obtained by graft copolymerizing a polyamide oligomer to a maleic anhydride graft modified resin of a β-unsaturated carboxylic acid ester copolymer resin, and a tackifier. Ethylene-vinyl ester copolymer resins represented by ethylene-vinyl acetate copolymer resins or ethylene-α,β-unsaturated carboxylic acid ester copolymer resins represented by ethylene-alkyl acrylate copolymer resins include A copolymer of about 5 to 50% by weight of vinyl ester or α,β-unsaturated carboxylic acid ester is used.
If the copolymerization ratio of these comonomers is lower than this, the adhesion will decrease, and conversely, if the ratio is higher than this, no particular improvement in adhesion can be expected, and instead the heat resistance will decrease. Become. Further, it is preferable to use these ethylene copolymer resins having a melt index of about 1 to 2000 dg/min, preferably about 20 to 1000 dg/min. The reaction of graft-modifying maleic anhydride onto these ethylene copolymer resins is carried out by a well-known method using an organic peroxide as a polymerization initiator. In this graft modification, maleic anhydride is used in an amount of about 0.1 to 5 parts by weight, preferably about 0.5 to 2 parts by weight, per 100 parts by weight of the ethylene copolymer. If maleic anhydride is used in a proportion smaller than this, the desired effect of improving adhesion will not be obtained, and the heat resistance will not improve as the number of reaction points in the polyamide oligomer decreases. On the other hand, even if more maleic anhydride is used than this, no further adhesion improvement effect will be obtained, and on the contrary, it will increase the melt viscosity of the graft-modified resin and, ultimately, the hot melt adhesive, making it difficult to work in the actual bonding process. make sex worse. The graft copolymerization reaction of the polyamide oligomer to the maleic anhydride graft-modified resin is carried out by the method described in the above-mentioned patent publication.
Examples of polyamide oligomers include lactams such as ε-caprolactam and ω-laurolactam, or ω-aminocarboxylic acids such as 6-aminohexanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. The polymer used is one in which an acid is polymerized and its terminals are capped with an aliphatic amine capping agent, and the average degree of polymerization is preferably about 4 to 6. If an adhesive with an average degree of polymerization lower than this is used, no improvement in heat resistance can be expected, and if an adhesive with an average degree of polymerization higher than this is used, the melt viscosity of the hot melt adhesive will increase and workability in the bonding process will be affected. make worse. These polyamide oligomers are used in a proportion of about 20 to 5 parts by weight, preferably about 15 to 7 parts by weight, relative to about 80 to 95 parts by weight, preferably about 85 to 93 parts by weight, of the maleic anhydride graft-modified resin. If less polyamide oligomer is used, no improvement in heat resistance is observed. On the other hand, if a larger amount of polyamide oligomer is used than this, the adhesiveness will be reduced. That is, the presence of an excess polyamide oligomer that does not react with maleic anhydride groups improves heat resistance but slightly lowers adhesiveness. Examples of tackifiers include hydrogenated glycerin esters (Arakawa Chemical's Ester Gum H, etc.), hydrogenated pentaerythritol (Arakawa Chemical's Ester Gum H, etc.)
HP, etc.), fully hydrogenated rosin (Rika Hercules product, Fural AX, etc.), terpene resin (cheap crude oil product, YS Resin, etc.), etc., which have good compatibility with the polyamide oligomer graft copolymer resin can be optionally used. . The polyamide oligomer graft copolymer resin and the tackifier are used in an amount of about 30 to 70 parts by weight. Outside this range, the heat resistance of the hot melt adhesive will be reduced or, conversely, the melt viscosity will increase, resulting in a reduction in workability in the bonding process. Hot melt adhesives can be prepared from both of these by adding a viscosity modifier such as wax, a high melt index ethylene-vinyl ester copolymer resin or an ethylene-α,β-unsaturated carboxylic acid ester copolymer resin, as necessary. After adding a heat stabilizer, an antioxidant, etc. thereto, it is heated to a temperature of about 140 to 240°C, preferably about 160 to 220°C, and kneaded. Next, the effects of the present invention will be explained with reference to Examples. Example 1 Ethylene-vinyl acetate copolymer resin (vinyl acetate content 28% by weight, melt index 150dg/
) 99 parts (weight, same below), maleic anhydride 1
1 part and 0.1 part of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 polymerization initiator were dry blended and kneaded at 240°C using a single screw extruder with an inner diameter of 30 mm. A maleic anhydride graft modified resin was produced. Separately, add 1000 g of ε-caprolactam, 5 ml of water and 400 ml of n-hexylamine to 2 volumes.
into an autoclave under a nitrogen atmosphere.
Stirred at 250°C for 18 hours. After cooling, the obtained polyamide oligomer was washed with hot water and then dried. In measuring the average degree of polymerization by neutralization titration of terminal amino groups,
This polyamide oligomer had a value of 4.6. To 90 parts of the above maleic anhydride graft modified resin,
10 parts of this polyamide oligomer were dry blended and kneaded at 210°C using the above single screw extruder.
A polyamide oligomer graft copolymer resin was produced. This polyamide oligomer graft copolymer resin
A hot-melt adhesive was produced by kneading 50 parts of the sample and 50 parts of a tackifier (Ester Gum H, manufactured by Arakawa Chemicals) at 200°C using a stainless steel beaker. This hot melt adhesive was evaluated by the following method, and the results are shown in Table 1 below. (a) Melt viscosity Measured at 180°C using a Bruckfield viscometer. (b) Ring and Ball Softening Point Measured according to the hot melt adhesive test method specified by the Japan Adhesive Industry Association. (c) T-peel strength The resin composition forming the hot melt adhesive was press-molded to form a press sheet with a thickness of about 0.2 mm. This press sheet was cut into a size of 25 x 150 mm and sandwiched between two aluminum plates with a thickness of 0.1 mm. This aluminum plate laminate, 200
After preheating for 1 minute by placing it on a hot plate at ℃,
A roller having a width of 45 mm and a weight of 2 kg was reciprocated once to perform thermocompression bonding, and then the laminate was turned over and the same thermocompression bonding was performed. The aluminum plates bonded together in this way were cut into 15 mm width pieces, and the T-peel strength was measured using an Autograph (manufactured by Shimadzu Corporation) at a peel rate of 200 mm/min, and the value was converted to a 25 mm width. . (d) Shear failure temperature Cut the press sheet into a size of 13 x 25 mm,
This is made into one aluminum plate (25 x 100 x 3 mm)
Place it in a thermostatic oven at 200℃ with another aluminum plate of the same size, and preheat for 15 minutes. After preheating, the two aluminum plates are crimped with a load of 2 kg so that the bonding area is 13 x 25 mm. If a 400g load is suspended on one side of the aluminum plate bonded in this way, and the temperature is raised stepwise from 40℃ by 5℃ over 20 minutes, the bond will break. Temperature was measured. Example 2 In Example 1, 100 parts of another ethylene-vinyl acetate copolymer resin (vinyl acetate content 28% by weight, melt index 400 dg/min) was used, and another polyamide oligomer (average degree of polymerization 5.6) was used. The same amount of ε-caprolactam oligomer) was used to make a hot melt adhesive. Example 3 In Example 1, the same amount of ethylene-ethyl acrylate copolymer resin (ethyl acrylate content 27% by weight, melt index 200 dg/min) was used instead of the ethylene-vinyl acetate copolymer resin, and the mixture was kneaded. A maleic anhydride graft modified resin was produced at a temperature of 250°C, and this was mixed with a polyamide oligomer.
A polyamide oligomer graft copolymer resin was obtained by kneading at 200°C, and a hot melt adhesive was similarly produced using this resin. Comparative example 1 Ethylene-vinyl acetate copolymer resin (vinyl acetate content 28% by weight, melt index 6dg/min)
50 parts and 50 parts of tackifier (Ester Gum H) were heated at 200°C in a stainless steel beaker.
A hot melt adhesive was prepared by mixing the two. Comparative Example 2 44 parts of the ethylene-vinyl acetate copolymer resin used in Example 1, 6 parts of another ethylene-vinyl acetate copolymer resin (vinyl acetate content 28% by weight, melt index 15 dg/min) and tackifier A hot melt adhesive was produced in the same manner as in Comparative Example 1 using 50 parts of Ester Gum H. Comparative Example 3 A commercially available polyamide hot melt adhesive (Tomide 535, manufactured by Fuji Kasei) was used. The measurement results in Examples 2 to 3 and each comparative example are also
It is shown in Table 1 below.

[Table] Comparative Example 1 above is a high viscosity hot melt adhesive using ethylene-vinyl acetate copolymer resin as the base polymer, and it has a low shear fracture strength of 70°C, which is an index of heat resistance. That of a similar low viscosity hot melt adhesive is 55°C, indicating an even lower heat resistance. Also, comparative example 3
The polyamide-based hot melt adhesive has low viscosity and extremely good heat resistance, but exhibits only a low T-peel strength. On the other hand, the hot melt adhesive according to the present invention has a melt viscosity of Comparative Example 1.
Although it shows a value between those of 2 to 2, it shows higher heat resistance than those, and the T-peel strength at room temperature also shows a value that is sufficient for practical use, and it is extremely excellent in terms of the balance of various properties. There is. This can be said to be an extremely important effect in actual use. Example 4 In Example 1, a maleic anhydride graft modified resin was produced using the same amount of another ethylene-vinyl acetate copolymer resin (vinyl acetate content 28% by weight, melt index 400 dg/min). and 5 parts of polyamide oligomer are kneaded to obtain a polyamide oligomer graft copolymer resin, and this and a tackifier are kneaded at 180°C using a Labo Plastomill.
A hot melt adhesive was produced by kneading the mixture. Example 5 In Example 4, 90 parts of maleic anhydride graft modified resin and 10 parts of polyamide oligomer were kneaded to obtain a polyamide oligomer graft copolymer resin, and a hot melt adhesive was produced in the same manner using this. Example 6 In Example 4, 80 parts of the maleic anhydride graft modified resin and 20 parts of the polyamide oligomer were kneaded at 200°C using a Laboplast Mill to obtain a polyamide oligomer graft copolymer resin, and this was used to make a hot melt adhesive. Manufactured. Comparative Example 4 In Example 6, 70 parts of maleic anhydride graft modified resin and 30 parts of polyamide oligomer were kneaded to obtain a polyamide oligomer graft copolymer resin, and a hot melt adhesive was produced using this. The measurement results in Examples 4 to 6 and Comparative Example 4 are as follows:
It is shown in Table 2 below.

[Table] From the above results, it can be seen that even if the proportion of the graft copolymerized polyamide oligomer is increased, the melt viscosity does not increase accordingly. this is,
The polyamide oligomer is stoichiometrically more abundant than the maleic anhydride sites to be reacted, and the polyamide oligomer remains mixed without reacting, and at a temperature of 180°C, it is in a molten state and the melt viscosity is lowered. There is. On the other hand, the T-peel strength decreases as the proportion of the graft copolymerized polyamide oligomer increases. In addition, the shear failure temperature, which is an index of heat resistance, is
It is highest when the proportion of polyamide used is about 10% by weight, and if it is outside the range of about 5 to 20% by weight, no effect of improving heat resistance can be expected, and on the contrary, adhesiveness decreases.

Claims (1)

[Scope of Claims] 1. A polyamide oligomer graft copolymer obtained by graft copolymerizing a polyamide oligomer to a maleic anhydride graft modified resin of an ethylene-vinyl ester copolymer resin or an ethylene-α,β-unsaturated carboxylic acid ester copolymer resin. A hot melt adhesive consisting of a polymeric resin and a tackifier. 2. Claim 1, which uses an ethylene copolymer resin copolymerized with about 5 to 50% by weight of vinyl ester or α,β-unsaturated carboxylic acid ester.
Hot melt adhesive as described in section. 3 Maleic anhydride modified resin is ethylene copolymer
The hot melt adhesive according to claim 1, which is a resin graft-modified with about 0.1 to 5 parts by weight of maleic anhydride per 100 parts by weight. 4 Polyamide oligomer has an average degree of polymerization of about 4 to 6
The hot melt adhesive according to claim 1, which is an ε-caprolactam oligomer. 5. The polyamide oligomer graft copolymer resin is a resin obtained by graft copolymerizing about 20 to 5 parts by weight of a polyamide oligomer to about 80 to 95 parts by weight of a maleic anhydride modified resin. Hot melt adhesive. 6 Polyamide oligomer graft copolymer resin approx.
A hot melt adhesive according to claim 1, comprising about 30 to 70 parts by weight of a tackifier and about 70 to 30 parts by weight of a tackifier.