JPS6231036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermal adhesive composition composed of a nylon copolymer and a modified ethylene vinyl acetate copolymer used for thermal bonding (so-called hot melt bonding). The aging stability after adhesion, which was a drawback of nylon copolymers, has been improved without impairing the
The object of the present invention is to provide a thermal adhesive composition with improved heat deterioration resistance, hot water resistance, chemical resistance, etc. Conventionally, polyethylene, ethylene/vinyl acetate copolymers, partially saponified products of these copolymers, ionomers, etc. have been used for thermal bonding, but they have poor adhesive strength and poor durability after bonding. There was a limit to this. Furthermore, nylon copolymers have relatively good heat adhesive properties and are expected to be used in a wide range of applications, but the following problems limit their application. (1) It has strong resistance to many chemicals, but has extremely low resistance to certain chemicals such as acids, alkalis, and hot water. (2) There is a limit to heat resistance. At temperatures above 80°C, deterioration due to oxidation is likely to occur in air. (3) Adhesive strength may decrease over time after adhesion. This phenomenon is remarkable in the case of metal materials with exposed adherends. In order to improve this problem, methods of blending modifiers have been studied or adopted. For example, polymeric modifiers include polyethylene, ionomers, ethylene/vinyl acetate copolymers, diallyl ester resins, and methoxymethylated nylon, and low molecular modifiers include organic phosphate esters, β-methylanthraquinone, and Danthrene, oxirane group-containing organosilicon compounds, benzenesulfone butyramide, etc. are used.
However, although such conventional modifiers can partially improve the problems of nylon copolymers mentioned above, they do not solve all the problems at the same time, and on the contrary, they inhibit the original performance of nylon copolymers. However, new problems often occurred. The present invention was made to eliminate the drawbacks of the prior art, and consists of 5 to 60% by weight of an ethylene/vinyl acetate copolymer modified with an unsaturated carboxylic acid or a derivative thereof, and the following A or /
and 4 to 95% by weight of the nylon copolymer B. A: A nylon copolymer having at least three types of repeating units selected from the following repeating unit groups. (a) [NH(CH ₂ ) _o CO] However, n is a positive integer of 5 to 11. (b) [NH(CH ₂ ) ₆ NHCO(CH ₂ ) _n CO] However, m is a positive integer from 4 to 12. B The next repeating unit, n of the repeating unit
Nylon copolymer containing 10 to 30% by weight of =5 and 70 to 90% by weight of n=11 [NH(CH ₂ ) _o CO] The nylon copolymer used in the present invention contains lactam or (and) nylon. Examples of nylon copolymers that can be made from salt and have three or more types of repeating units of A include nylon 6,66,
310 copolymer, nylon 6,66,11 copolymer, nylon 6,66,12 copolymer, nylon 6,66,
610,11 copolymer, nylon 6,66,610,12 copolymer, nylon 6,66,612 copolymer, nylon 6,69,12 copolymer, nylon 6,612,12 copolymer, etc. I can give it to you. Examples of copolymer compositions preferably used in such copolymers include those shown in copolymer examples "A" to "C" in Table 1. Further, as the nylon copolymer B, there are those shown in the copolymer example "d" in Table 1.

[Table] The nylon copolymer used in the present invention has normal crystallinity, and is a low crystallinity with a degree of crystallinity of 20% or less. When forming a film from the composition of the present invention, the work can be carried out smoothly if the degree of crystallinity is controlled during the manufacturing process, as will be described later. The nylon copolymer used in the present invention has a latent heat of crystal fusion of 3ca/g after crystallization due to ease of handling.
More preferably, it is 5 cal/g or more. The latent heat of crystal fusion is a useful physical property for determining the crystal state and can be measured using a differential scanning calorimeter or the like.
Furthermore, the melting point of the nylon copolymer used in the present invention is
Preferably below 170℃. Thermal bonding can be performed at a temperature below the thermal change temperature of commonly used adherend materials. The modified ethylene/vinyl acetate copolymer used in the present invention is an ethylene/vinyl acetate copolymer containing an unsaturated carboxylic acid or a derivative thereof through copolymerization or graft copolymerization. Alternatively, the content of the derivative is preferably 0.001% to 10% by weight in the modified polymer. If the content is less than this range, the effect of improving the heat deterioration resistance, hot water resistance, chemical resistance, and stability over time after adhesion of the nylon copolymer will be significantly reduced, and if it exceeds this range, the water resistance and hot water resistance of the adhesive will be significantly reduced. becomes worse.
Examples of unsaturated carboxylic acids or derivatives thereof used for modifying ethylene/vinyl acetate copolymers include maleic acid, itaconic acid, fumaric acid, citraconic acid, and acid anhydrides, esters, amides, imides, etc. of these unsaturated carboxylic acids. There are derivatives such as metal salts. The modified ethylene/vinyl acetate copolymer preferably has a vinyl acetate content of 0.5 to 75% by weight. In the composition of the thermal adhesive of the present invention, if the modified ethylene/vinyl acetate copolymer is 5% by weight or less, the nylon copolymer's heat deterioration resistance, hot water resistance, chemical resistance, and stability over time after adhesion are reduced. The improvement effect is small.
When the amount exceeds 60% by weight, the chemical resistance, hot water resistance, and heat retention of adhesive strength become worse than that of a single nylon copolymer. A mixture of two or more of each of the nylon copolymer and modified ethylene/vinyl acetate copolymer used in the adhesive composition of the present invention can also be used. Further, various additives (stabilizers, lubricants, antiblocking agents, tackifiers, plasticizers, etc.) and polymers can be added to the composition of the present invention within a range that does not significantly change the adhesive performance. Stabilizers that are effective in the compositions of the present invention include phenolic, amine, and copper compound substances, such as 1,3,5-trimethyl-
2,4,6-tris[3,5-di-tert-butyl-4-hydroxybenzyl]benzene, 2,4-
Bis(n-octylthio)-6-(4'-hydroxy-3',5'-di-tert-butylanilino)-1,
3,5-triazine, tetrakis [methylene-3
-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate] methane, octadecyl-3-(3,3-di-tert-butyl-4-hydroxyphenyl)propionate, copper naphthenate , copper iodide, hypophosphate, and diphenyl phosphonate. Such stabilizers range from 0.01% to 2% by weight of the composition of the invention, in particular
Favorable results are obtained when it is added in a range of 0.05% to 0.5% by weight, and the heat resistance after bonding is further improved. The adhesive composition of the present invention preferably has a film shape. A convenient way to form a film is to melt the adhesive composition using an extruder, extrude it from a die, and then cool and solidify it. If the extruded film sticks to a cooling drum or the like and is difficult to remove, it is recommended to extrude the composition onto a release paper (film) or form a composite film directly with a resin having good release properties. Such a film manufacturing method can be operated smoothly by controlling the crystallinity of the nylon copolymer in the composition at each step. For example, it is preferable that the latent heat of crystal fusion of the nylon copolymer in the composition does not exceed 1.0 cal/g until the adhesive composition is extruded from an extruder and wound into a laminated film or composite film. This prevents peeling between film layers and air intrusion into peeling gaps during film forming and taking-off work, and provides a film with excellent flatness without surface defects such as air marks. The laminated film or composite film that has been formed has a high melting latent heat of nylon copolymer in the adhesive composition.
After crystallizing to a concentration of 1.5 cal/g or more, preferably 3 cal/g or more, the adhesive composition film may be peeled off to form a single-layer film. It is non-sticky and has a low coefficient of friction, making it easy to unwind the film.
Handling work during slitting work and thermal bonding processing becomes easier. In composite extrusion or extrusion onto release paper, it is desirable that the latent heat of crystal fusion of the nylon copolymer does not exceed 1.0 cal/g until the film is wound and film formation is completed. To control this, it is necessary to pay attention to the temperature and water absorption conditions during the process of cooling and solidifying the film and until winding. An example of preferable conditions is that the temperature of the nylon copolymer is not allowed to rise above the glass transition temperature from film casting to winding, or that even if the temperature rises, it is suppressed within several minutes. The nylon copolymer in the laminated film or composite film is 1.5 cal/g or more, preferably 3 cal/g.
Crystallization to a higher level can be achieved by adjusting the temperature and humidity conditions. When the temperature is below the glass transition temperature of the nylon copolymer and in a low humidity atmosphere, crystallization hardly progresses and it may even take several months to achieve the desired degree of crystallinity. Although it varies depending on the composition of the nylon copolymer, a temperature of 40° C. or higher is preferable to promote crystallization. Also, leave it in a high humidity atmosphere or sprinkle water on it.
Crystallization can be promoted by spraying etc. If the adhesive composition film of the present invention is rolled up at the final stage of the film forming process and left for at least 5 to 48 hours before handling, all subsequent operations will be carried out smoothly. For example, film slits, laminated films and composite film separates,
This is in the process of thermal bonding. This was an unexpected effect, but it is thought to be due to various effects other than the crystallization of the nylon copolymer, such as mixing of the resins, changes in the affinity state, and relaxation of stress generated during film formation. Seem. The adhesive composition of the present invention can be laminated with an olefinic copolymer such as an ethylene copolymer containing an ionomer or a polyolefin derived from an unsaturated carboxylic acid or its derivative to form a composite film-like thermal adhesive. It is useful for thermal bonding of dissimilar materials such as non-polar materials such as polyolefin materials and materials made of glass, metals, and polar polymers. The thermal adhesive composition of the present invention exhibits excellent performance in adhering fibers, metals, wood, leather, glass, polymer molded products, etc., for example. As detailed above, since the present invention uses a thermal adhesive composition comprising a modified ethylene/vinyl acetate copolymer and a nylon copolymer, the adhesive strength tends to decrease over time after the adhesive processing. Adhesion of metal materials, adhesion of clothing that requires harsh water resistance, hot water, and dry cleaning resistance for washing, adhesion of various equipment and containers for the chemical industry and agriculture that require chemical resistance. It has excellent effects on adhesion of building materials, automobile parts, interior parts, etc., which require water resistance, heat resistance, and durability. In addition, the composition of the present invention makes it possible to perform thermal bonding at the lowest possible temperature, which is the most difficult problem in thermal bonding, and to have the highest possible bonding heat resistance after bonding, thereby significantly increasing the application of thermal bonding. This has the excellent effect of expanding the Example 1 The following three types of compositions were prepared. Composition: Crystalline nylon copolymer with a melting point of 115°C (composition: 30% by weight nylon 6, nylon 610
(38% by weight, 12% by weight of nylon 66, 20% by weight of nylon 12). Composition: 80% by weight of nylon copolymer in the composition
20% by weight of ethylene/vinyl acetate copolymer (with vinyl acetate content of 8%). Composition: 80% by weight of nylon copolymer in the composition
, maleic anhydride grafted ethylene/vinyl acetate copolymer (maleic anhydride content 1.5
% by weight, vinyl acetate content 8% by weight)
Contains 20% by weight of Note that this modified ethylene vinyl acetate copolymer was modified based on the ethylene vinyl acetate copolymer of the composition. However, "composition" is a comparative example, and "composition" is an example of the present invention. Next, a polypropylene film was used as a release film, and each composition was extruded onto the film using an extruder at an extrusion temperature of 185°C using the so-called extrusion lamination method to a thickness of 50 μm to form a laminated film. It was rolled up into a roll. The drum used to cool the extruded film circulated water at 25°C. The temperature of the film at the time it left the cooling drum was 27-29°C. The temperature of the winding roll is also within this range. A layer of the composition was removed from the film immediately after being rolled out, and the latent heat of crystal fusion of the nylon copolymer was measured using a differential scanning calorimeter.
It was hot at g. During film formation, the film formation process could be carried out smoothly without peeling of the laminated film or partial entrapment of air. The laminated film was placed in an atmosphere of 50°C.
I left it for a while. After the treatment, the film made of the composition was taken out and the latent heat of crystal fusion of the nylon copolymer was measured and found to be 9 cal/g or more. An operation was carried out to separate each nylon copolymer layer from the polypropylene film. There was no resistance during peeling, and the nylon copolymer composition film could be rolled up smoothly without deformation. Further, even when the film was left in a roll after being rolled up, no blocking occurred. The following adhesion tests were conducted on the three types of film compositions obtained as described above. (1) Adhesion method Stainless steel sheet (SUS#304, thickness 0.2mm)
After washing with trichlene, each nylon copolymer composition film was sandwiched between two stainless steel sheets and pressed together using a hot plate under the following conditions. One-sided heating, hot plate temperature 160℃, heating and pressing time 30 seconds, pressure 500g/cm ² (2) Adhesion measurement method After leaving the adhesive piece under the conditions shown in Table 2, peel it at an angle of 180° and measure the adhesive strength. Measure. (3) Adhesion Measurement Results As shown in Table 2, the compositions corresponding to the examples of the present invention were found to have excellent heat deterioration resistance after adhesion, hot water resistance, and chemical resistance.

[Table] Example 2 The following compositions were blended in the proportions shown in Table 3,
The obtained compositions were prepared as shown in Table 3.
〜〓、〓〜〓. Composition: Crystalline nylon copolymer with a melting point of 120°C (composition: 30% by weight nylon 6, nylon 66
(20% by weight, 50% by weight of nylon 12) Composition: Ethylene vinyl acetate copolymer (vinyl acetate content 15% by weight) Composition: Maleic anhydride grafted ethylene/vinyl acetate copolymer (maleic anhydride content (1% by weight, vinyl acetate content: 15% by weight) This modified ethylene/vinyl acetate copolymer was modified based on the composition. Next, each composition in Table 3 and isotactic polypropylene were directly combined in a die at an extrusion temperature of 210°C using two extruders to form a composition layer with a thickness of 50μ and polypropylene layer thickness of 40μ. The film was extruded using a casting method using a cooling drum so that the polypropylene layer touched the drum. Water at 25° C. was circulated through the drum, and the temperature of the film was 26 to 29° C. when the film was separated from the cooling drum. The temperature of the winding roll is also within this range. The layer of the composition was taken out from the composite film immediately after being rolled up, and the latent heat of crystal fusion of the nylon copolymer was measured using a differential scanning calorimeter, and it was found to be 0.15 cal/g. The composite film had good adhesion and could be formed smoothly. The composite film was left in an atmosphere at 45°C for 48 hours. An operation was performed to separate each nylon copolymer composition layer from the polypropylene layer. There was no resistance during peeling, the nylon copolymer composition film could be smoothly rolled up without deformation, and there was no blocking even when the winding roll was left standing. The following adhesion test was conducted on each of the film compositions obtained as described above. (1) Adhesion method A film composition was sandwiched between two aluminum sheets (thickness: 2 mm) and pressure bonded. Other conditions were the same as in the above adhesive method. (2) Adhesion measurement method After leaving the adhesive piece in the following conditions, measure the peel adhesion strength at a 90° angle. (a) Initial bond strength: Measured immediately after the bonding process is completed. (b) Aging acceleration treatment: When a nylon copolymer adhesive is used for metal bonding, the adhesive strength decreases over time and reaches saturation at a certain point (approximately 10 days at 20℃), but when heat treated at 70℃, the heating time increases.
The time course can be accelerated in 30 minutes.
Measured in an atmosphere of 20℃ after treatment. (c) Heat resistance of adhesion: Adhesion strength in an atmosphere of 70℃. The test piece was measured after undergoing the aging acceleration treatment described above. (d) Heat deterioration resistance: After being left in an atmosphere of 85℃ for 7 days, the adhesive strength was measured. (3) Adhesion measurement results As shown in Table 3, the composition consists of
Compositions 〓, 〓, 〓 whose blending ratios were within the range of the present invention gave excellent results in that the adhesive strength was stable under various conditions.

[Table] Comparative Example 1 A composition was prepared in which 80% by weight of the nylon copolymer used in Example 1 was blended with 20% by weight of polyethylene grafted with 1.5% by weight of maleic anhydride or similarly modified polypropylene. A film with a thickness of 50 μm was obtained by processing in the same manner as in 1. The film was used for thermal bonding of stainless steel sheets in the same manner as in Example 1 to obtain a bonded product. The processed product was prepared in Example 1.
The samples were left in hot water at 85°C under the same conditions as shown in Table 2, and their hot water resistance was examined, and the results shown in Table 4 were obtained. The composition of the comparative example had poor hot water resistance and did not far match the performance of the composition of the present invention.

[Table] Items left for a while.
Comparative Example 2 Modified ethylene/vinyl acetate copolymer used in Example 1
A blended composition consisting of 20% by weight and 80% by weight of nylon 6 (melting point 215°C) or nylon 12 (melting point 180°C) was prepared and extruded using an extruder to make a 50μ film. This film was used to bond aluminum sheets in the same manner as in Example 2, but a high heat bonding temperature was required and workability was extremely poor. Table 5 shows the results of aging acceleration treatment of the adhesive processed product.
As shown in Figure 3, the adhesive strength was significantly reduced by the treatment and the adhesive performance was poor.

[Table] For the adhesive processed product of this comparative example (no aging acceleration treatment was performed), the adhesive strength after being left in an acetic acid aqueous solution and the adhesive strength in an atmosphere of 70°C was measured using the adhesiveness measurement method of Examples 1 and 2. It was measured. The results are shown in Table 6.

[Table] Example 3 Two adhesive compositions 〓 and 〓 shown in Table 7 were blended using the composition of Example 2. A laminated film was obtained by composite extrusion with isotactic polypropylene in the same manner as in Example 2. Similarly post-treated the compound film layer (thickness 50
μ) was peeled off from the polypropylene layer. Aluminum sheets were adhered using the blend film under the same conditions as in Example 2. The adhesive processed products were evaluated by the adhesion measuring method of Examples 1 and 2. The results are shown in Table 7. The composition of the present invention has superior adhesive strength in a high temperature atmosphere and after immersion in chemicals compared to the comparative example. The comparative example is significantly inferior in such performance. In particular, the low adhesive strength measured under high temperature atmosphere is noticeable.

[Table] Comparative Example 3 Ethylene vinyl acetate copolymer (vinyl acetate content 15% by weight) (composition) and maleic anhydride grafted ethylene vinyl acetate copolymer (maleic anhydride content 1% by weight, vinyl acetate Content 15
A 2 mm thick aluminum sheet was adhered in the same manner as in Example 2 using a 50 μm thick film of (wt%) (composition). Adhesive processed products are Examples 1 and 2.
Evaluation was made using the following measurement method. The results are shown in Table 8. Adhesion strength in high temperature atmosphere and after immersion in chemicals are significantly lower.

【table】

Claims (1)

[Claims] 1. 5 to 60% by weight of ethylene/vinyl acetate copolymer modified with unsaturated carboxylic acid or its derivative
and a nylon copolymer of A or/and B below
40-95% by weight of a thermal adhesive composition. A: A nylon copolymer having at least three types of repeating units selected from the following repeating unit groups. (a) [NH(CH ₂ ) _o CO] However, n is a positive integer of 5 to 11. (b) [NH(CH ₂ ) ₆ NHCO(CH ₂ ) _n CO] However, m is a positive integer from 4 to 12. B The next repeating unit, n of the repeating unit
A nylon copolymer containing 10 to 30% by weight of =5 and 70 to 90% by weight of n=11. [NH( _CH2 ) _o CO]