JPH0441226A - Method for bonding plastic - Google Patents

Abstract

PURPOSE:To enhance bonding strength by thinly applying an org. compound having an epoxy group and an unsaturated group in its molecule or an org. compound having an amino group or an alkoxysilane group and an unsaturated group in its molecule to the surface of plastic as bonding pretreatment and irradiating the same with far infrared rays. CONSTITUTION:When an adhesive to be used is an epoxy type in bonding plastic, an org. compound having an unsaturated group and an epoxy or amino group in its molecule is thinly applied to the surface of an object to be bonded and, when an adhesive is a silicone type, an org. compound having an unsaturated group and an alkoxysilane group in its molecule is thinly applied to the surface of the object to be bonded. The coated part is irradiated with far infrared rays and the unsaturatd group of the treatment agent is grafted to the surface of plastic and either one of the epoxy group, the amino group and the alkoxysilane group is formed to the treated surface of plastic. These functional groups form a covalent bond along with the adhesive to enhance the bonding strength at an interface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pretreatment method for bonding plastics.

[Conventional technology]

Conventionally, plastics, especially plastics with a high degree of crystallinity and polyolefin plastics, have been considered difficult to adhere to. In order to improve these adhesive properties, measures have been taken to modify the plastic surface.

Many studies have been conducted on surface modification methods to improve the adhesiveness of plastics, but methods using far ultraviolet light are attracting attention because they are simple and highly effective. For example, in JP-A-60-166332, the surface of a molded article of a propylene polymer composition is irradiated with low-pressure mercury lamp light in an attempt to improve adhesion, printability, and paintability.

Also, JP-A-60-226534 and JP-A-60
In Japanese Patent No. 245643, a synthetic resin molded body is irradiated with far ultraviolet rays using a laser, and a similar effect is obtained.

There are also cases where the surface modification effect was further improved by treating plastics before irradiating them with far ultraviolet rays. In JP-A-01-9243, a surface-active molded product is produced by irradiating ultraviolet rays of a specific wavelength onto the surface of a molded product of a low-active polymer material whose surface has been swollen by contacting an ultraviolet absorbing solvent under heating. I am getting .

All of these methods are simple and highly effective, but the effectiveness is low depending on the adhesive used, and in particular, a sufficient effect was not obtained when bonding using a silicone adhesive. Furthermore, when using an epoxy adhesive, which is the most commonly used structural adhesive, a fairly high contact strength is generally required. In this case, the above method also shows a considerable improvement in adhesive strength, but sufficient strength for structural adhesion is not obtained.

[Problem to be solved by the invention]

As mentioned above, conventional bonding methods, particularly bonding using silicone adhesives and epoxy adhesives, have a problem in that sufficient strength cannot be obtained.

This invention was made to solve the above-mentioned problems, and by using a treatment method that is optimal for the type of adhesive, the adhesive strength can be further improved.

[Means to solve the problem]

In the plastic bonding method according to the present invention, as a pretreatment for the bonding process, if the adhesive is silicone-based, an unsaturated group and an alkoxy Si group are added to the molecule, and if the adhesive is epoxy-based, an unsaturated group is added to the molecule. By applying a thin layer of an organic compound having an amino group or an epoxy group and irradiating it with far ultraviolet rays, the adhesive strength is increased compared to untreated or simply treated with far ultraviolet rays.

[Effect]

The plastic adhesion method in this invention uses an organic compound that has an unsaturated group and an epoxy group or an amino group in the molecule if the adhesive used is an epoxy-based adhesive, or an organic compound that has an unsaturated group in the molecule if the adhesive is a silicone-based adhesive By applying a thin layer of an organic compound containing alkoxysilane groups and alkoxysilane groups to the surface of the adherend, and then exposing the coated area to far ultraviolet rays, the unsaturated groups of the treatment agent will graft onto the plastic surface, and the treated plastic surface will be coated with Either an epoxy group, an amino group, or an alkoxysilane group is formed, and these functional groups form a covalent bond with the adhesive to improve adhesive strength at the interface.

〔Example〕

An epoxy adhesive refers to a composition containing one or more types of compounds having at least one epoxy group, and the epoxy group in the system is ring-opened at room temperature, heat, light, or radiation. It can be cured by Furthermore, among the compounds in the same section that have an unsaturated group and an epoxy group in the molecule, the most readily available and cheapest are glycidyl acrylate and glycidyl methacrylate. Sufficient effects can be obtained using these compounds. In addition, itaconic acid monoglycidyl ester, butenetricarboxylic acid monoglycidyl ester, butenetricarboxylic acid diglycidyl ester, butenetricarboxylic acid glycidyl ester, butenetricarboxylic acid triglycidyl ester, 2-
Methyl allyl glycidyl ether, styrene-p-glycidyl ether, 3,4-epoxybutene, 3,4-epoxy-3-methyl-1-butene, 3,4-epoxy-
Examples include 1-pentene, 3,4-epoxy-3-methylpentene, 5,6-epoxy-1-hexene, vinylcyclohexene monoxide, and p-glycidylstyrene. Furthermore, by acrylic modification of a part of the epoxy group of a commercially available polyfunctional epoxy compound, a compound having an epoxy group and an acrylic group in the molecule can be obtained.

Silicone adhesives refer to those having siloxane bonds in their cured products, and include addition type, dealcoholization type, oxime removal type, acetone removal type, and acid type.

In addition, compounds having an alkoxysilane group and an unsaturated group in the molecule are those included in the late production of silane coupling agents, and the alkoxysilane groups include methoxysilane group, ethoxysilane group, propyloxysilane group, and methoxyethoxysilane group. The unsaturated group is preferably an acrylic group, a methacryl group, a vinyl group, or an allyl group. Preferred commercially available products include vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltripropoxysilane, allyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

The viscosity of these compounds is preferably 1000 cps or less; if it exceeds that, it will be difficult to apply a thin film.

It becomes difficult to express the effect. Moreover, it is preferable to apply these compounds after diluting them with a solvent to 0.5 to 20%; if the concentration of the treatment liquid is too high, it will be difficult to apply a thin film.

Application methods include spin cord, spray, and depping, as well as methods using felt or cotton swabs.

After application, sufficient drying is required to volatilize the solvent component.
Preferably, drying at .degree.

After the solvent dries, the surface of the substrate is irradiated with far ultraviolet rays.

Any light source that emits far ultraviolet light may be used, but considering efficiency, price, and stability, low-pressure mercury lamps,
Xenon-mercury lamps and excimer lasers are preferred. Irradiation intensity is 1-100 mW/am2 at 198 nm
The irradiation energy is preferably 10 to 5000 mJ/CM2.

The irradiation atmosphere varies depending on the type of substrate, but the effect is greater in an inert gas atmosphere than in air. However, even when irradiated in air, a sufficient improvement in adhesive strength can be seen.

If the treated base material is left as it is, the treatment effect will gradually be lost, so it is preferable to bond the base material as soon as possible.

The effective time for the treatment effect varies depending on the substrate, the type of treatment liquid, and the environment of the place where it is left, but it is 0.5 to 12 hours as a refreshment.

Next, in order to clarify the above embodiment, specific examples based on the above embodiment will be described, but the scope of the present invention is not limited to these specific examples.

Adherent used in Examples pps (polyparaphenylene salvoid Asahi Glass)
RE-04), PC (polycarbonate, Mitsubishi Gas Chemical Co., Ltd., ml), and LCP (liquid crystal polymer, A215, manufactured by Polyplastics Co., Ltd.), each with a length of 10
A plate formed to have a diameter of 0 mm, a width of 12.5 mm, and a thickness of 3.5 m was used.

Adhesive AV-138 (two-component epoxy resin manufactured by Ciba Geigy) used in the examples
, Bond MO8-10 (2-component epoxy resin Konishi (
(manufactured by Shin-Etsu Chemical Co., Ltd.), KE-1830 (one-component addition type silicone adhesive manufactured by Shin-Etsu Chemical Co., Ltd.), KE-41 (one-component acetic acid-removed silicone adhesive manufactured by Shin-Etsu Chemical Co., Ltd.) Example 1 A 5% glycidyl methacrylate inpropatol solution was applied thinly to the above PPS, PC, and LCP using a cotton swab. At this time, the solvent evaporates immediately after application.

Next, it was irradiated with a 450W low-pressure mercury lamp for 30 seconds in a nitrogen atmosphere. At this time, the distance between the low-pressure mercury lamp and the sample was 3 an.

Using the three types of samples subjected to such treatment, simple lap adhesive test pieces (adhesive area 12°5 x 12.5 mm) were prepared between the same types. The types of adhesives used were Araldite AV-138 and MOS-10, and both were cured at room temperature for 24 hours.

Each sample prepared under these conditions was PP5-1.
．． PC-1 and LCP-1.

Example 2 A 5% isopropanol solution of vinylmethoxysilane was applied thinly to PPS, PC, and LCP using a cotton swab, and a low-pressure mercury lamp was irradiated under the same conditions as in Example 1 to prepare a simple lap test piece. However, the adhesives used were KE-1830 and KE-41, and the former was cured at 120°C for 12 hours, and the latter was cured at room temperature for 1 week. The samples prepared in this way were each treated as PP5-2. P
C-2°LCP-2.

As a comparison of the above samples, untreated samples and samples prepared with low pressure mercury lamp treatment (in air) were prepared as PP5-R1 and P5-R1, respectively.
C-R1, LCP-R1, PPC-R2, PC-R2,
It is called LCP-R2.

Adhesive Strength Measurement Results Tables 1 and 2 show the results of measuring the tensile shear strength of the prepared samples. (Pulling speed: 51IllllZ minutes) From these results, it can be said that the surface treatment method according to the present invention is a further improvement over the conventional method.

Table 1 Table 2 [Effects of the Invention] As described above, according to the present invention, as a pretreatment for bonding plastics, after applying a thin layer of an organic substance having an unsaturated group and irradiating it with far ultraviolet rays, it is possible to This has the effect of producing plastics that exhibit excellent adhesion to other adhesives.

Claims (1)

[Claims] In an adhesive method in which plastics are bonded using an epoxy adhesive or a silicone adhesive, the plastic surface is treated with an organic compound having an epoxy group and an unsaturated group in the molecule, or an amino group or A plastic bonding method that involves applying a thin layer of an organic compound containing an alkoxysilane group and an unsaturated group and then irradiating it with far ultraviolet rays.