RU2143451C1 - Composition for making adhesive melts and method of preparation thereof - Google Patents

Abstract

FIELD: chemical industry, more particularly, constructional adhesive melts for adhesive bonding of various sorbents which comprise ethylene-vinyl acetate copolymer and filler which comprises amorphous silicon dioxide. SUBSTANCE: described is method of preparing adhesive melts by applying filler onto surface of copolymer granules. EFFECT: reduced cost price of production, higher adhesion to degreased surfaces of various substrates. 5 cl, 6 tbl

Description

 The invention relates to a technology for manufacturing structural hot melt adhesives and can be used for adhesive bonding of various substrates in aviation, mechanical engineering, electronics, electronics, the furniture industry, packaging and household use.

Known / Chemical Encyclopedia (Ed. By I.L. Knunyants. - M .: Soviet Encyclopedia 1990, vol. 2, p. 409); D.A. Kardashov. Construction adhesives. - M.: Chemistry. - 1989 -396 p .; Adhesives and Adhesive Compounds (Ed. H.-S. Lee) Translated from English. - M .: World. 1991, p. 226 / widespread use of hot-melt adhesives (adhesives, sealants, compounds) based on a thermoplastic copolymer of ethylene and vinyl acetate in various fields. The main advantages of these hot melt adhesives are high adhesion to various substrates, short curing times, excellent water-chemical-bio-mechano-shock and vibration resistance, durability under extreme conditions (radiation and UV radiation, thermal cyclic loads, peak shock accelerations, low temperatures up to -60 ^o C). In order to increase the main operational indicators (adhesive and cohesive strength, bonding speed, heat resistance, adaptability of adhesive application, etc.) functional additives (rosin and its esters, low molecular weight polystyrene, atactic polypropylene, acrylic acid and its derivatives are introduced into the composition of adhesive compositions , caprolactam and oligomeric polyamides, indencumarone and phenolic resins, maleic or phthalic anhydrides, various types of wax, diactyl phthalates, polyisocyanates, polyurethanes, bonfire oil and other substances) and fillers (talc, mica, kaolin and other aluminosilicates; ground quartz sand; chalk, dolomite, magnesite; rutile; wood flour and other highly dispersed materials). Fillers are introduced into hot-melt adhesive compositions, as a rule, in order to increase heat resistance and hardness, to reduce shrinkage and residual internal stresses, but above all to reduce production costs.

 The most common among domestic hot melt adhesives are: KRUS-1 (TU 13-936-86), KRUS-2 (TU 13-0273250-32-92), KRPEM-1 (TU OP 13-0274186-88), KRKP ( TU OP 13-027325018-88), as well as adhesives of the TKM (VPKTIM), GIPK-143, TK-2P, 327/10 grades, PKS-25 wax alloy. It should be noted that all the hot melt adhesives listed above contain at least three components: a polymer matrix, a filler, and a functional additive.

 Composite (filled) hot melt adhesives based on polyolefins and their derivatives are also widely used abroad / Adhesives and adhesive compounds (Edited by H.-S. Lee) Translated from English. - M .; Peace. 1991.S. 226; Vaganai B. Industrial application of structural hot-melt adhesives - Zh.: Materials and Technologies, 1990. v. 78, 3-4, p. 67-70; The use of oligomers as adhesives (Onisi Reji, Hatisu Ainti, Gijutsu Shira) Mitsubishi Sekiyu Kabushiki Kaysia. - 1990, N 74 - 32-39. - RJChem. 1991, 2T256; US patent N 48718. Hot melt adhesives (Gako M., Kinbara H., - Mitsubishi Gas Chemical Company.) 08/23/88. Publ. 10/03/89 Priority N 60-219254 (Jap.) Dated 10/03/85 - RZHKhim., 1991, 7T337P .; Structural adhesives and their application (Eur. Adhes and Sealats. - 1994, 11, N 2, p. 23./. Among the best samples of foreign ethylene vinyl acetate (EVA) hot-melt adhesives objectively should include: "Kleiberite" (Germany), "Bostik "(Great Britain), Elvax-II and Marlex (USA), UHU (Taiwan). Mandatory components of adhesive compositions are fillers and adhesive, plasticizing or viscous additives, the total amount of which, as a rule, is in the range of 3-7 . Unfilled hot-melt adhesives are used limitedly due to their high cost and inconsistencies of parameters with stringent operational requirements of international standards.

 The manufacturing technology of domestic and foreign hot melt adhesives is traditional and includes the operation of mixing the molten (softened) polymer (copolymer) with fillers and functional additives as a mandatory operation. It should be emphasized that the operation of mixing the components of the composition in the molten polymer matrix is quite energy-intensive and technologically complex, because It requires heating and temperature control of the adhesive mass, the use of injection molding or extrusion machines, special screw mixers, installations for cooling and granulation. All this significantly increases the cost of adhesives.

As an analogue of the inventive hot melt adhesives, hot melt adhesive compositions according to Japanese application / JP 64-33349 (Sekisut Kaganu Koge KK) 1991 /, including (wt.), Can be used: copolymer of 10-35% vinyl acetate with ethylene - 100 : agent (LA) that improves the stickiness of the composition with a softening point of 50-60 ^o C (rosin and its derivatives, polyterpene oil, coumaronindene, phenolic, styrene and dicyclopentadiene resins - 5-150; waxy substance (paraffin and microcrystalline waxes, chlorinated paraffins, low molecular weight polyethylene, atactic polypropylene) - 10-60; emollient (polybutene, dioctyl and dibutyl phthalates, flowing esters, rosins, low molecular weight styrene resins, chloroparaffin hydrocarbons); fillers (chalk, clay or talc); antioxidants (phenolic, amine or sulfur-containing substances). These hot melt adhesives have good adhesion to paper, films of polypropylene, polyesters, polyamides, cellophane, non-woven materials and other substrates.

The disadvantages of the KR / JP 64-33349 (Sekisut Kagan Koge K.K.) 1991 / include:
- a large number of components used;
- the complexity and energy intensity of manufacturing technology;
- limited scope (mainly the production of heat-sensitive adhesive tapes).

 As a close analogue of the claimed invention, it is possible to consider the domestic hot melt adhesive KRUS-2 / Hot melt adhesive KRUS-2 TU 13-0273250-32-92 / manufactured by Polymer JSC (Vakhtan, Nizhny Novgorod Region), including a copolymer of ethylene with vinyl acetate as an adhesive matrix, adhesive, plasticizing, thermostabilizing additives and a combined binary finely divided filler obtained by mechanical mixing of these components in a molten polymer base.

The main disadvantages of the adhesive composition analogue of KRUS-2 / Hot melt adhesive KRUS-2 TU 13-0273250-32-92 / are:
- a large number and scarcity of a number of components used and the high cost of production resulting from these circumstances;
- the complexity and energy intensity of the manufacturing process, leading to an additional increase in the cost of adhesive granules;
- a narrow range of glued substrates recommended by the Technical Conditions (steel, wood, press materials, paper);
- the high (from 12.1 to 14.8 million rubles / 1 ton as of October 1, 1997) contractual price of hot-melt glue on the Russian market and the associated restriction on the sale of this type of product;
- low softening temperature of the adhesive according to Martens (85 ^o C), which does not meet the requirements of a number of technological processes, for example, in the manufacture of air filters.

 The closest technical solution in relation to the claimed invention is a hot-melt adhesive composition / JP 63-130558 (Ninpon gosey kagaku koge K.K.) 1989 /, proposed by Japanese authors, including (wt.): Copolymer of ethylene with vinyl acetate - 100; reinforcing fibrillated fibers from polyolefins and their block copolymers with styrene, acrylonitrile, vinyl chloride, vinyl acetate, alkyl (meth) acrylates, hydrophilized with polyvinyl alcohol and its derivatives, starch or cellulose derivatives - 2-20; filler (chalk, talc, rutile, clay) - 100-400. The total solids content in the composition is 60-75%.

 The technology for the production of Japanese hot melt adhesives, as well as domestic, provides for the operation of mixing the components of the composition in the melt of the copolymer matrix with all the ensuing negative consequences.

However, along with the advantages of the prototype composition / JP 63-130558 (Ninpon gosey kagaku koge K.K.) 1989 / has the following disadvantages:
- hot melt adhesives have a high cost due to the complexity and energy consumption of the manufacturing process, the high cost and the large number of components used, for example: fibrillated fibers, internal adhesive additives;
- prototype adhesives have poor adhesion to metals and alloys, in particular to their non-degreased surfaces; mainly concrete, dry plaster, PVC tile, foamed PS sheets, press materials are subject to bonding.

 All this limits the scope of the composition of the prototype and inhibits its widespread commercial distribution.

The aim of the present invention is:
- reducing the cost of production of hot melt adhesives by reducing the number of components used to two and significantly simplifying the technology for their manufacture;
- expanding the scope of application of hot melt adhesives by increasing the range of glued substrates, including ferrous and non-ferrous metals, ceramics, press materials, concrete, wood, rubber, plastics, glass, paper, cardboard, etc .;
- a noticeable increase in adhesion to oily (non-degreased) surfaces of various substrates, primarily metals, while maintaining high cohesive physical, mechanical and other performance indicators.

 This goal is achieved by introducing into the copolymer of ethylene and vinyl acetate products containing amorphous silicon dioxide in optimal dosages, or by surface treatment of the granules of the copolymer with these products.

As the polymer base (matrix), the authors used a granular copolymer of ethylene with vinyl acetate containing 5-30 wt. % vinyl acetate with a melt flow index of 5-1750 g / 10 min, a density of 0.925-0.950 g / cm ^3, respectively (TU 6-05-1636-97). The fillers were various types of natural (tripoli, diatomite, flask) and synthetic (silica gel technical grades ASM and KSMG in accordance with TU 3956-76; aerosil grades A-380, A-175 in accordance with GOST 14922-77, methylaerosil grades AM-1-300 in TU U-6-057431.60.005-95; white carbon black grade BS-50 according to TU 18307-78) silicon dioxide (silica) with a particle size in diameter of not more than 100 microns. To obtain convincing evidence of the right choice of products containing an amorphous form of silica as fillers for hot melt adhesives and the convenience of comparing the results, the authors tested the effectiveness of introducing chemically bonded aluminosilicate forms of silicon dioxide into the polymer matrix (kaolin grade KS-1 according to GOST 21286-82 , talc in accordance with GOST 21235-75, muscovite mica in accordance with GOST 14307-82, construction clay in accordance with TU 14-8-152-75) and crystalline form of silicon dioxide (quartz sand in accordance with GOST 8736-77 and river sand OST 8736-85). It should be emphasized that no other substances, except for the copolymer of ethylene with vinyl acetate and fillers containing silica, were not introduced into the compositions of the studied adhesive compositions.

 Information on the mass content of pure silica in the studied fillers and the specific surface area are presented in table. 1.

 As can be seen from the table. 1, products containing an amorphous form of silicon dioxide (silica gels, aerosil, white soot, tripoli, diatomite, flask), regardless of the mass percent of silica in them, have a high specific surface area (from 3.5 to 520 sq / g) . Products containing silicon dioxide in chemically bound (kaolin, talc, mica) or crystalline (quartz sand) states, as a rule, have a small specific surface area (from 0.18 to 1.3 sq / g).

 The difference in the specific surface area between products with amorphous silica, on the one hand, and products with chemically bonded or crystalline silica, on the other hand, is apparently the decisive factor affecting the adhesive properties of the hot melt adhesives under study.

 In the table. 2 and 3 show the adhesive characteristics (shear strengths in the systems (galvanized steel / galvanized steel and st3 / st3) of the claimed compositions obtained by introducing products containing silicon dioxide into the volume of the copolymer melt and onto the surface of its granules without melting the latter. Determination of values ultimate shear strength was carried out according to GOST 14759-69. For ease of comparison of adhesive parameters in the same table 2 the experimental values of standard tensile strengths for shear are given. (Cruz 2113-27) and foreign ( "Kleiber", Germany, "Bostic" United Kingdom, Taiwan UHU) hot melt adhesives, as well as Japanese authors reproduced the adhesive composition of the prototype.

Comparative analysis of the data table. 2 and 3 allows us to draw the following unambiguous conclusions:
1. The highest adhesion shear strength in galvanized steel / galvanized steel and STZ / STZ systems, regardless of surface condition, is achieved in compositions based on SEV-11306- (075) using synthetic amorphous silica having highly developed (175-520 sq. m / g) surface: silica gel and aerosil (methylaerosil), provided that they are applied to the surface of the copolymer granules. A positive effect of the influence of amorphous silicon dioxide on the adhesive properties of hot melt adhesives is achieved by applying it to the surface of granules in an amount of 0.2-0.6 wt.h. ^*
2. The introduction of products containing amorphous forms of silicon dioxide (silica gel, aerosil, white soot, tripoli, etc.) onto the surface of the granules of the copolymer matrix leads to a noticeable increase in the adhesion of hot melt adhesives to oily (non-degreased) surfaces of galvanized and ordinary steel. The positive effect of the introduction of these products, apparently, is ensured by the absorption of oil into the volume of amorphous silica during the bonding of substrates and the renewal of their surface, as well as through the chemical interaction of active silica with metal oxides (zinc, iron, etc.) with the formation of silicates at elevated bonding temperatures.

 3. Amorphous forms of silica contained in the claimed (studied) products in optimal (about 3 parts by weight) dosages have a positive effect on the adhesion of hot melt adhesives to oily St3 and galvanized steel even if they are introduced directly into the melt volume, although the effect is not so significant compared to surface application. In general, the traditional technology of mixing the copolymer and fillers in the melt in this case can be applied. However, in this case, the dosage of the filler (optimally 3 wt.h) should be strictly observed in the range of 0.4-5%. When the maximum (5%) is exceeded, the adhesion characteristics of hot melt adhesives deteriorate. Small doses of filler in the melt volume (less than 0.4 wt.h) (see table. 2) do not provide the necessary positive effect.

^* Note: Satisfactory adhesion of silica particles on the surface of the copolymer granules, according to the inventors, is ensured, firstly, by the action of electrostatic attraction forces, and secondly, due to the capillary forces of highly porous fillers.

 4. Products containing silicon dioxide in chemically bound (aluminosilicates) or crystalline (quartz sand, river sand) forms do not provide a positive effect either in volume or on the surface of the matrix and therefore cannot be recommended for practical use.

 In the table. 4 presents the economic calculations of the contractual prices of the claimed compositions in comparison with the prices of prototype and standard, domestic and foreign hot melt adhesives. Data analysis table. 4 allows us to verify that the hot melt adhesives proposed by the authors of the present invention with the new method for their production have a much lower cost compared to similar ones and for this reason can be used for commercial distribution.

 In the table. 5 presents high-quality adhesive indicators of the inventive hot melt adhesives, determined in accordance with GOST 15140-78 to various substrates: brass, rubber, chipboard, polyvinyl chloride (PVC) edge, filter paper, lavsan film, etc. How seen from the table. 5, the adhesives proposed by the authors have a satisfactory adhesion (3-5 points) to the majority of the investigated substrates and are not inferior to domestic and foreign analogues, which allows us to recommend these adhesives for practical use in mechanical engineering, the rubber industry, furniture manufacturing and in everyday life.

 In support of the above, the inventors conducted a production check of the quality of gluing by the inventive hot melt adhesives of galvanized steel and paper curtains of filter elements of various types of air purifiers. The test results of the tensile strength according to GOST 1497-73 are presented in table. 6. As can be seen from the table. 6, the adhesion parameters of the claimed KR to oiled zinc. steel turned out to be significantly higher than the parameters of control samples of filter elements of air purifiers with polyolefin hot-melt adhesive (GOST 16337-77 grade 16803-070) used by the enterprise. In addition, the separation occurred on a paper curtain, and in the case of control samples on metal, which proves the clear advantages of the new CD.

 Thus, it is proved that when using the inventive compositions and the inventive method for producing hot-melt adhesives, a noticeable decrease in the cost of adhesive products is achieved by reducing the number of components used and simplifying the manufacturing technology of KR, expanding the range of functional applications of hot melt adhesives by increasing the range of glued substrates and simplifying gluing technology the creation of the possibility of connecting oily (non-degreased) surfaces, eliminating the degreasing operation tions.

 The following are specific examples of the manufacture of the inventive hot melt adhesives, illustrating the simplification of the technology for their preparation.

 Example I. The granules of a copolymer of ethylene and vinyl acetate are loaded into a mixer, in which the matrix is heated to a transition to a liquid viscous state. In the melt obtained in small portions with stirring, a metered amount of a product containing amorphous silicon dioxide is added. Mixing continues until a homogeneous adhesive mass is obtained, which is then pressed through a die, cooled and granulated.

 Example II The copolymer granules (particles) are loaded into an unheated mixer, into which a product containing amorphous silicon dioxide is poured out at room temperature. The system is mixed for 5-30 minutes until a uniform filler layer is obtained on the surface of the copolymer granules. Then the resulting mixture is poured onto the grid and shaken to remove excess filler mass. The modified granulate remaining on the grid is used as intended.

Claims (1)

1. Composition for the production of hot melt adhesives, comprising a copolymer of ethylene with vinyl acetate and a filler, characterized in that as a filler it contains products containing amorphous silicon dioxide, in the following ratios of components, parts by weight:
Ethylene Vinyl Acetate Copolymer - 100
Amorphous Silica Product - 0.4 - 5.0
2. A method of producing a hot melt adhesive, comprising mixing a copolymer of ethylene and vinyl acetate with a filler, characterized in that they are mixed by applying a filler, products containing amorphous silicon dioxide, to the surface of the granules of a copolymer of ethylene and vinyl acetate.

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