JPH011781A - Crosslinkable hot melt adhesive composition, adhesive obtained therefrom, and method for adhering the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a crosslinkable hot melt adhesive composition comprising an ethylene-vinyl acetate copolymer containing primary hydroxyl functionality and a blocked polyisocyanate. This composition is used as a tackifying resin (tackifier)
In combination with this, it is possible to create an adhesive that can withstand high temperatures.

Prior art adhesives are typically liquid and, after application, solidify to bond the surfaces to be adhered. Generally, this solidification occurs due to polymerization or polycondensation of the main components of the adhesive. Furthermore, solid adhesive compositions have been studied for a long time. That is, hot melt adhesives that are solid at room temperature and that are based on thermoplastic resins that have adhesive properties are also being investigated.

This adhesive is turned into a fluid by heating, and when it solidifies again by cooling, the surfaces to be adhered are bonded. These hot melt adhesives are generally formed by combining two main components, a thermoplastic resin and a tackifying resin (tackifier), to which are further added waxes, stabilizers, fillers, plasticizers, etc. agents can be added.

Problems to be Solved by the Invention At present, these hot melt adhesives exhibit excellent adhesive properties, but have the disadvantage of poor heat resistance and cannot exceed temperatures of 70 to 80°C. The most widely known thermoplastic resins as main components are polyamide, active polypropylene, and especially ethylene-vinyl acetate copolymer.

An object of the present invention is to provide a hot melt adhesive composition that has excellent heat resistance and can maintain adhesive strength up to a temperature of 200 to 220°C.

Means for Solving the Problems The hot melt adhesive composition provided by the present invention has a first
The main component is a combination of ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) having hydroxyl groups and blocked polyisocyanate. Generally, an adhesive resin (tackifier) is further added to the EVA-polyisocyanate composition to produce an adhesive.

The EVA used in the compositions of the present invention is a copolymer of ethylene, vinyl acetate, and an ethylene-based monomer having at least one primary hydroxyl group.

This EVA can be obtained by grafting a copoly7-nihy1'oxylated ethylene monomer of ethylene and vinyl acetate by a known method.

Grafting is generally carried out by solution radical polymerization, suspension polymerization or melt mass polymerization. The above polymers can also be prepared by direct polymerization of the three monomers using the most advantageous processes known.

Among the abovementioned ethylenic monomers having at least one primary hydroxyl group, preference is given to using hydroquine ethyl acrylate and hydroquine ethyl acrylate, but it is also possible to use monomers of the following formula: R1CH2'' CHR3CH20H F2 However, in the above formula, -R, is a hydrocarbon residue or hydrogen, -R2 is hydrogen or a methyl group, and -R3 is an ester group, an amide group, or an alkyl group.

Examples of these ethylene monomers include allyl alcohol, oleyl alcohol, and N-hydroxymethylacrylamide.

The composition of EVA is the initial monomer weight ratio of 45 to 93% by weight of ethylene, 5 to 40% by weight of vinyl acetate,
It is a combination of 2 to 15% by weight of ethylenically unsaturated monomers having at least one hydroxyl group. This EVA contains 2 Xl per 100 g of copolymer.
Preferably it contains from 0-2 to 15X10-' moles of primary 0H groups.

The EVA described above is combined with a blocked polyisocyanate to form an adhesive composition. Polyisocyanate means a polyfunctional compound having at least two -NCO functional groups in one molecule. The polyisocyanate can be selected from aliphatic, cycloaliphatic, aromatic and/or heterocyclic polyfunctional incyanates, but among the best known are toluene diisocyanate, diphenylmethane diisocyanate, hexane diisocyanate, etc. Diisocyanates such as methyl diisocyanate or inphorone diisocyanate are preferred. These polyisocyanates are introduced into the composition in blocked form. Blocked polyisocyanate refers to multiple -
By this we mean polyisocyanates in which the NCO functional groups are reversibly linked to each other and/or via suitable compounds called pro-7tation agents. The polyisocyanate blocking agents are generally used in combination with active hydrogen and therefore preferably with phenols, alcoholoberactams, oximes or secondary amines.

Examples of blocking agents include 2,6-di-tert-butyl-4-methylphenol, 4-tert-butylphenol,
m-cresonope4,4-thiobis(3-methyl-6-
Mention may be made of tert-butylphenol and ε-caprolactam or benzophenoxime. However, it is preferred to use tackifying resins (tackifiers) as blocking agents in order to enhance the final adhesive properties of the compositions. The tackifying resin (tackifier) is selected among resins having free functional groups capable of blocking incyanate functional groups. - For boat fishing, tackifying resins (tackifiers) with free phenolic groups, especially terpene-phenolic resins, are used. The molecular weight of this terpene-phenolic resin generally ranges from 500 to 5000 and is produced by copolymerizing a phenolic compound with a terpene derivative.

Blocked polyisocyanates are stable at room temperature and under heat and can be mixed into EVA at elevated temperatures without being esterified, as long as the temperature is below that at which the -NCO functionality becomes unblocked. It is effective to mix this blocked polyisocyanate with EVA in such a ratio that the ratio of the blocked -NCO group in the polyisocyanate to the 10H group in the EVA is from 0.61 to 1. This premix becomes the crosslinkable hot melt adhesive composition that is the object of the present invention. This premix can be stored for long periods of time.

The composition of the present invention is combined with a tackifying resin (tackifier) to form a hot melt adhesive with excellent heat resistance. The amount of tackifying resin (tackifier) to the composition is determined by the EV
Preferably from about 0 to 70 parts by weight per 100 to 30 parts by weight of the A-block isocyanate composition. The tackifying resin (adhesive agent) gives hot melt adhesives better adhesion and usually has a molecular weight of about 400 to 250.
0 low molecular weight compounds are used. As their name suggests, these tackifying resins exhibit tackiness due to the property of either a high degree of plasticization of the polymeric composition or limited compatibility with the polymeric composition. These tackifying resins (tackifiers), which are themselves well known, are broadly divided into three types: corophanes (resins), their hydrogenated and modified derivatives, maleic oxides and esters, terpene resins, and petroleum resins. Separated. Petroleum resins include aliphatic ones, aromatic-modified aliphatic ones, and hydrogenated petroleum resins.

When the polyisocyanate of the above composition is blocked by a tackifying resin (tackifier), it is not necessarily necessary to add the tackifying resin (tackifier), and this composition can be used directly as an adhesive. can be used.

However, even in this case, -NCO of the polyisocyanate
This does not mean that tackifying resins (tackifiers), the same or different from those used as functional group blocking agents, should not be added to the composition.

It is of course also possible to incorporate the above-mentioned conventional additives into the adhesive of the invention.

The resulting adhesive is used at high temperatures, especially at 130° C., which is the temperature at which the blocked polyisocyanate begins to dissociate and its original functional groups are liberated. In other words: It is used at a temperature at which the block is unblocked and the free isocyanate functionality regenerates, whereby the primary hydroxyl functionality of the EVA reacts with the isocyanate, resulting in cross-linking of the EVA, which unexpectedly results in the known Compared to other hot melt adhesives, the heat resistance of the adhesive of the present invention is definitely improved.

The unblocking of incyanate and the crosslinking reaction with hydroxyl groups is facilitated by the use of catalysts. The catalyst is generally a metal salt such as a tin salt or a tertiary amine such as dibutyltin dilaurate (DLDBSn
), diazabicyclooctane (DABCO), etc.

The invention will become clearer from the following examples.

However, these Examples do not limit the present invention in any way.

Example 1 4,4-diphenylmethane diisocyanate blocked with a terpene-phenolic tackifying resin (IJRAVAR 75205 from 05M) in a reactor with a capacity of 2β equipped with stirring means and heating means. (MDI) and introduced in the following order: 480 g of terpene-phenolic resin.

Xylene 1.3A, toluene 0.1β, MDI 75g0 The temperature is maintained at 60°C until the resin and polyisocyanate are completely dissolved. Thereafter, the temperature is gradually increased to 120° C. and maintained at that temperature for 2 hours. Upon cooling, the solution is poured into an aliphatic hydrocarbon. The precipitated -64 product is also filtered and dried under vacuum.

The adhesive composition is a type 50 cylindrical Brabender (BRABII:NDER) plastograph with a capacity of 60.
Prepare in a tank. Add each compound in the following order.

That is, EVA, a tackifying resin (tackifier) added as necessary, and then blocked polyisocyanate. This mixture is stirred at 100° C. for 10 minutes, optionally in the presence of DLDBSn.

This mixture is placed between two aluminum plates and the whole is compressed at a pressure of 0.1 MPa for 5 minutes at 160° C. in test 1.3.7 and at 180° C. in test 2.4.5.

Adhesive properties are evaluated by: Peel: ASTM Standard D 1876 Shear Method: ASTM Standard D 1002 Flow Method:
S, A, F, T.

In the S, A, F, T, Flow method, a weight of I kg is suspended on the sample prepared for the shear test, and the whole is placed in a furnace programmed to heat the sample at a rate of 5°C/1 minute.

S, A, F, and T are the temperatures at which bonds break. By this measurement, the maximum operating temperature of the adhesive can be determined.

Example 2 A replica is produced in the same manner as in Example 1 using MDI blocked by ε-caprolactam under the following conditions.

Blocked with caprolactam in a 1β reactor equipped with stirrer and heating device, 4.4'-
Prepare diphenylmethane diisocyanate (MDI).

The reactor is introduced in the following order: Caprolactam 118.65 g.

2-Ethoxyethyl acetate) 95g0 The temperature is kept at 60°C until the caprolactam is completely dissolved and then lowered to room temperature. Then, while stirring, a solution of 131.25 g MDI and 394 g 2-ethoxyethyl acetate is slowly added.

Gradually heat up to 70°C. At this temperature, the blocked isocyanate precipitates. The precipitate is filtered, washed with hexane and dried under vacuum at 40°C.

Test 6.8.9 involves compression between aluminum plates at 160°C.

The compositions and test results of the two examples are shown in the table below.

Table 1 EV8: 72% by weight of ethylene and 23% by weight of vinyl acetate
Terpolymer block with 5% by weight of ethyl acrylate for hydroquine! al A: MDI blocked with phenolic terpene resin DERTOPHENE T:
DRT's phenolic terpene resin

Claims (10)

[Claims] (1) A crosslinkable hot melt adhesive composition containing an ethylene-vinyl acetate copolymer as a main component, characterized in that a blocked polyisocyanate is combined with an ethylene-vinyl acetate copolymer having a primary hydroxyl group. Composition. (2) The ethylene-vinyl acetate copolymer having primary hydroxyl groups as described above contains 45 to 93% by weight of ethylene, 5 to 40% by weight of vinyl acetate, and 2 to 15% by weight of at least one primary hydroxyl group. 2. A composition according to claim 1, characterized in that it is obtained in combination with an ethylenically unsaturated monomer having . (3) The ethylene-vinyl acetate copolymer having primary hydroxyl groups as described above has primary hydroxyl groups of 2 x 10^-^2 to 15 x 10 per 100 g of the copolymer.
The composition according to claim 1 or 2, characterized in that it contains ^-^2 mol. (4) The first O of the above ethylene-vinyl acetate copolymer
4. Composition according to any one of claims 1 to 3, characterized in that the ratio of blocked -NCO functional groups of the polyisocyanate to H groups ranges from 0.1 to 1. (5) The blocked polyisocyanate is mixed with the ethylene-vinyl acetate copolymer having the primary hydroxyl group at a temperature below the temperature at which the -NCO functional group becomes unblocked. from 4
The composition according to any one of the above. (6) The composition according to any one of claims 1 to 4, wherein the polyisocyanate is blocked by a tackifying resin (tackifier). (7) In a crosslinkable hot melt adhesive mainly composed of an ethylene-vinyl acetate copolymer and a tackifying resin (tackifier), the vinyl acetate is combined with a blocked polyisocyanate having a hydroxyl group. An adhesive characterized by: (8) The adhesive according to claim 7, wherein the tackifier resin (tackifier) serves as a blocking agent for the polyisocyanate. (9) an ethylene-vinyl acetate copolymer having a hydroxyl group and a blocked polyisocyanate;
An adhesion method comprising heating a crosslinkable hot melt adhesive comprising a tackifying resin (tackifier) to a temperature equal to or higher than the unblocking temperature of the -NCO functional group of the polyisocyanate. (10) The method according to claim 9, characterized in that the hot melt adhesive is heated to a temperature of 130° C. or higher.