JPS61218674A - Polyurethane adhesive having suppressed residual tackiness after curing - Google Patents

Abstract

PURPOSE:To obtain the titled novel adhesive free from residual tackiness after hardening and useful for flexible printed circuit board, by compounding an organic solvent with a diisocyanate derivative and a cellulose derivative soluble in said solvent. CONSTITUTION:The objective adhesive can be produced by compounding (A) an organic solvent with (B) a diisocyanate derivative and (C) a cellulose derivative soluble in the component A. The component B is preferably the one produced by the polycondensation reaction of a diisocyanate and glycol, composed of the structural unit of formula (R1 and R2 are hydrocarbon residue) and having relatively high molecular weight.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a novel polyurethane adhesive that prevents tackiness remaining after adhesive curing.

(b) Problems to be Solved by the Prior Art and the Invention In recent years, polyurethane adhesives have been used to bond various articles due to their excellent performance. With the expansion of such application fields, residual tackiness after adhesive curing has become a problem, which was not considered a problem at all in the past. This residual tackiness is thought to be caused by the residual terminal NC groups of the diisocyanate derivative that is the main component of the polyurethane adhesive and the NGO groups of the triisocyanate compound that is the curing agent.

This problem is particularly important in the field of flexible printed wiring boards where the polyurethane adhesive is exposed after curing. In other words, a flexible printed wiring board is created by laminating a support such as a film and metal foil with a polyurethane adhesive, and then etching away the metal foil that becomes the non-wiring area, leaving the wiring area. However, the polyurethane adhesive after curing will be exposed in the non-wiring areas. Therefore, if there is residual tackiness in the polyurethane adhesive after curing, the wiring boards may stick to each other while the flexible printed wiring boards are stacked and transported. This adhesion reduces the commercial value of the flexible printed wiring board, and if the adhesion is significant, the wiring portion may peel off or the wiring board itself may be torn when it is removed.

Therefore, the present invention has been made with the aim of solving the drawbacks that have arisen with the expansion of the field of application of polyurethane adhesives, which did not exist in the past. The purpose is to prevent residual tackiness.

(c) Means and action for solving the problem, that is, the present invention provides a polyurethane system which prevents residual tackiness after curing and is made of an organic solvent and a diisocyanate derivative and a cellulose derivative that are soluble in the organic solvent. This relates to adhesives.

The polyurethane adhesive according to the present invention is of a room temperature or heat curing type, and hardens as the organic solvent evaporates.

The organic solvent used in the present invention is toluene.

Ethyl acetate, amyl acetate, butanol, ethanol, etc., as desired, may be used alone or in combination, and must be capable of dissolving both the diisocyanate derivative and the cellulose derivative. Therefore, depending on the type of diisocyanate derivative and cellulose derivative used, it is necessary to appropriately select or mix an organic solvent to dissolve them well.

Diisocyanate derivatives refer to relatively high-molecular-weight derivatives having the following structural units, which are mainly produced by the polyaddition reaction of diisocyanates and glycols.

(However, R, and R are hydrocarbon groups.) However, the diisocyanate derivatives referred to in the present invention also include those having a urethane bond +NHCOO+ and having a relatively high molecular weight and produced by other methods.

Ethyl cellulose is a cellulose derivative.

Nitrocellulose, cellulose acetate, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, etc. are used. This type of cellulose derivative is used alone as an adhesive by dissolving it in an organic solvent, but the present invention is characterized in that this substance is used as an anti-adhesion agent.

That is, after curing the diisocyanate derivative, the remaining N
It functions to block the GO group and prevent its tackiness.

The amount of the cellulose derivative to be blended may be as small as 0.5 to 3 parts by weight per 100 parts by weight of the diisocyanate derivative. This is because the amount of remaining NGO groups is small in the first place.

In the polyurethane adhesive of the present invention, a curing agent such as a diisocyanate compound or a triisocyanate compound is blended, as in conventional adhesives.

(d) Effects of the Invention As is clear from the above description, the use of the polyurethane adhesive according to the present invention has the effect of preventing tackiness of the adhesive after curing.

In particular, if the polyurethane adhesive according to the present invention is used to bond the film and metal foil of a flexible printed wiring board, the flexible printed wiring boards created by etching away the metal foil in the non-wiring areas can be immediately stacked and manufactured. This has the effect that it can be shipped as If this is a conventional polyurethane adhesive, it cannot be stacked immediately, so it is aged at high temperatures for more than 10 days before being stacked and shipped. As can be seen from this, the present invention is extremely useful from an industrial and economic perspective.

Claims (1)

[Claims] A polyurethane adhesive that prevents residual tackiness after curing and is made of an organic solvent and a diisocyanate derivative and a cellulose derivative that are soluble in the organic solvent.