JP3255773B2 - Pretreatment method for difficult-to-bond materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for pretreating an adherend,
More specifically, the present invention relates to a method for pretreating an adherend capable of improving the adhesiveness of a poorly adhesive material such as polyolefin.

[0002]

2. Description of the Related Art Polyolefins are roughly classified into lower olefin polymers and higher olefin polymers. Typical polymers of lower olefins are polyethylene and polypropylene, but these have excellent physical properties, are easy to process and have a wide range of uses, and are therefore injection-molded into car bumpers, food containers, pipes, etc. It is spun and widely used for tire cords and the like. Examples of higher olefins include poly (1-butene) and poly (4-methylpentene). These higher olefins are excellent in mechanical strength and dielectric properties, do not react with other than strong oxidizing agents, are easy to process, and can be used for fibers, films, injection molding and the like. In recent years, polyolefins having such properties have been increasingly used as automotive parts, structural materials, building materials, and the like due to demands for weight reduction.

[0003]

However, polyolefins have drawbacks such as poor dyeability due to lack of polar substituents in the polymer, and poor adsorption to metals and other plastics due to low polarity. . In particular, when molded and used alone, for example, when used by bonding to plastics, metals, etc., such as composite structural materials such as seat cushion covers and bumpers as automobile parts, the problem of poor adhesion is a problem. Become. Adhesion is an interface phenomenon, and it is essential that the surface of the adherend be wet by the adhesive. Therefore, the strength of the adhesive force varies depending on the degree of wetting of the surface of the adherend.

Consider a case where a low-polarity polymer such as polyolefin is bonded using a polyurethane-based adhesive.
These low-polarity polymers cannot react with the NCO of the polyurethane adhesive as they are, since there is no water attached to the surface as in the case of a metal oxide film. Polyolefin cannot form an oxide film, a polar group, or the like on its surface even after acid treatment. Therefore, when a polyolefin is adhered, the surface oxidation is extremely insufficient by wet treatment such as acid treatment, and the surface is oxidized by various dry treatments, for example, irradiation with plasma or ultraviolet (UV). Then, a treatment has been performed in which a polar group is provided on the surface so that van der Waals force and hydrogen bonding work. However, these treatments alone do not sufficiently oxidize the surface of the polyolefin and do not sufficiently form a polar group or a functional group, so that the adhesive strength may be insufficient, and further improvement in adhesiveness has been desired. We have already disclosed in Japanese Patent Application No. 4-283109 a pretreatment method for an adherend in which a photopolymerization initiator is applied to the surface of the adherend, and a primer containing an isocyanate component is applied after ultraviolet irradiation. I have. Here, a remarkable improvement was observed in the ordinary adhesive strength, but in some cases, the adhesive strength was not sufficient in water-resistant adhesion or the like.

[0005]

Means for Solving the Invention Accordingly, the present inventors have
The inventors of the present invention have conducted studies on a bonding method for bonding a difficult-to-bond material such as polyolefin with a polyisocyanate-based adhesive, and have completed the present invention. The present invention provides a method for attaching a pretreatment composition to the surface of an adherend, irradiating it with ultraviolet light, applying a primer, and adhering a poorly adherent material.

That is, in the first invention, a pretreatment composition containing a photopolymerization initiator having no hydroxyl group and a fluorescent dye is adhered to the adherend surface of the adherend, followed by irradiating with ultraviolet light and then isocyanate. A pretreatment method for bonding an adherend, characterized by applying a primer containing a component. The second invention is to apply a pretreatment composition containing a photopolymerization initiator having no hydroxyl group to the adherend surface of the adherend, then irradiate with ultraviolet light, and then apply a primer containing a fluorescent dye and an isocyanate component. This is a pretreatment method for bonding an adherend, characterized by applying. Here, the content of the photopolymerization initiator having no hydroxyl group in the pretreatment composition used in the first and second inventions is preferably 0.5 to 50% by weight, and The content of the fluorescent dye added to either the pretreatment composition or the primer is 0.1.
It is preferably from 0.01 to 2% by weight.

Hereinafter, the present invention will be described in detail.

The adherend using the pretreatment method of the present invention is of low polarity such as polyolefin, and specifically, is a polyethylene resin, a polypropylene resin, a poly-1-butene resin, a poly-4-methyl- 1-pentene resin and the like are preferred.

In a broad sense, the photopolymerization initiator blended in the pretreatment composition of the present invention absorbs light and directly decomposes,
Or a substance that is excited by light and interacts with a monomer or an appropriate electron donor, an electron acceptor, etc. to generate a primary radical effective for initiating polymerization and to initiate polymerization, It can be divided into a photodecomposition type photopolymerization initiator and a photoexcitation type photopolymerization initiator. The polymerization with the photopolymerization initiator proceeds by radical polymerization using any of the above photopolymerization initiators. The primary radical is generated when a molecule in a photodecomposed or excited state extracts a hydrogen atom from a hydrocarbon to generate a hydrocarbon radical. After the generation of the primary radical, polymerization proceeds by radical addition or radical abstraction in which the radical is added to an unsaturated bond. If the photopolymerization initiator according to the present invention does not have a hydroxyl group,
Any of a photodecomposition type initiator and a photoexcitation type initiator may be used.

[0010] As a photo-decomposition type initiator,

Embedded image (Here, R ^{1 to} R ^{4 each} represent a hydrogen, an alkyl group, or an aryl group.)

Specifically, 2,2-diethoxyacetophenone, benzyl methyl ketal, benzyl-β-methoxyethyl acetal, benzoin (2-phenyl-2
-Hydroxyacetophenone), benzoin alkyl ether, 2-hydroxy-2-methyl-propiophenone, 4'-isopropyl-2-hydroxy-2-methyl-propiophenone, 1-hydroxycyclohexylphenyl ketone, and the like. . Benzyl methyl ketal, benzoin alkyl ether and the like are particularly preferred.

The photo-excitation type photopolymerization initiator has a

Embedded image (Here, R ^{1 to} R ⁸ represent a hydrogen, an alkyl group, an aryl group, or a halogen atom, and l to r represent an integer of 0 to 5).

Specifically, benzophenone, methyl o-benzoylbenzoate, bis (4-dimethylaminophenyl) ketone, 4,4'-bisdiethylaminobenzophenone, 4,4'-dichlorobenzophenone, benzyl,
Acetophenone, p-dimethylaminoacetophenone,
Examples thereof include pt-butyltrichloroacetophenone, pt-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, chlorothioxanthone, 2-isopropylthioxanthone, and α, α-dichloro-4-phenoxyacetophenone. Benzophenone, thioxanthone, 4,4'-dichlorobenzophenone, chlorothioxanthone and the like are particularly preferred.

Such a photopolymerization initiator can be dissolved in a solvent, and the surface of the adherend can be treated with this solution.

The solvent that can be used in the pretreatment composition of the present invention is appropriately selected from those that can dissolve the photopolymerization initiator. Specifically, benzene, xylene, aromatic hydrocarbons such as toluene, acetone, methyl ethyl ketone, ketones such as methyl isobutyl ketone, methyl acetate, esters such as ethyl acetate, diethyl ether,
Examples thereof include ethers such as tetrahydrofuran and dioxane, and alcohols such as methanol, ethanol, and isopropanol.

The photopolymerization initiator compounded in the pretreatment composition of the present invention is usually dissolved in an amount of about 0.5 to 50% by weight when the solvent is 100% by weight. It is preferable to dissolve in the range of 1 to 20% by weight.

A fluorescent dye is added to the pretreatment composition or primer of the present invention. A fluorescent dye may be added to both the pretreatment composition and the primer. The initial adhesion is improved by adding a fluorescent dye. When added to the pretreatment composition, the initial adhesion is significantly improved as compared to when added to the primer. On the other hand, when carbon is blended in the primer, the water-resistant adhesion is improved whether the fluorescent dye is added to the pretreatment composition or to the primer. In this case, when a fluorescent dye is added to the primer, the improvement in water-resistant adhesiveness is large. The fluorescent dye added here is not limited by the structure, but specifically, 7-amino-4-trifluoromethylcoumarin, 7-ethylamino-6-methyl-4-trifluoromethylcoumarin. Coumarins such as 7-dimethylamino-4-trifluoromethylcoumarin, benzoxazine derivatives such as Lumilux manufactured by Rieder de Haen, and oxazole compounds such as Kayalite manufactured by Nippon Kayaku. .

The fluorescent dye to be added to the pretreatment composition of the present invention usually causes an increase in adhesion and a precipitation of the fluorescent dye itself when the total amount of the pretreatment composition is 100. Is added in the range of 0.01 to 2% by weight, which is not in the range, and is dissolved in the solvent. In particular, the range of 0.1 to 1% by weight is preferable. The reason for this is that, in terms of solubility in a solvent, an excessive amount causes precipitation.

The primer of the present invention contains an isocyanate compound or the like whether or not the fluorescent dye is contained. Here, as the isocyanate compound,
4,4'-diphenylmethane diisocyanate (MD
I), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), hydrogenated (hydrogenated) MDI, hydrogenated TDI, hydrogenated XDI, isophorone diisocyanate (IPDI), aromatic aliphatic Examples thereof include polyisocyanate, aromatic polyisocyanate, triphenylmethane triisocyanate, tris-p-isocyanate phenyl thiophosphate, and the like, and a mixture thereof as appropriate. In particular, a combination of MDI, tris-p-isocyanate phenylthiophosphate and aromatic isocyanate is preferable.

The fluorescent dye may be any coumarin-based, benzoxazine-derivative, or oxazole-based compound that is the same as that in the pretreatment composition. Particularly, a coumarin compound is preferable. Its content is 0.01-2% by weight
It is preferable that

When the fluorescent dye is contained in the primer of the present invention, the ratio of the fluorescent dye to the isocyanate compound can be appropriately set according to the type of the isocyanate component and the fluorescent dye. 10 primers
When it is 0, the amount of the fluorescent dye added is 0.01 to 2% by weight, preferably 0.1 to 1% by weight. The reason for this is that an excessive amount causes precipitation due to the solubility of the fluorescent dye in the solvent.

The primer of the present invention can contain various solvents which are inert to isocyanate groups. Specifically, ethyl acetate, methyl ethyl ketone, acetone, toluene and the like are preferable. The amount of the solvent is appropriately determined depending on the type of the isocyanate compound and the like.
About 1000 parts by weight is preferred.

The primer of the present invention may contain carbon in order to improve the water-resistant adhesion. If too much carbon is blended, uniform dispersion of the carbon in the primer becomes impossible, and clogging or the like may occur during kneading, which may cause a failure. About 50 to 200 parts by weight.

Various catalysts can be added as an optional component to the primer used in the present invention. Examples of the catalyst include amine catalysts such as triethylenediamine, pentamethylenediethylenetriamine, morpholine amine, and triethylamine, and tin catalysts such as octyltin didilaurate, dibutyltin dilaurate, and stannas octoate.

In the primer used in the present invention,
In order to obtain good workability, a urethane resin such as a polyester polyurethane resin and a polyether polyurethane resin, or a polyester resin can be blended. The amount of these resins is usually about 10 to 30 parts by weight based on 100 parts by weight of the isocyanate compound.

Further, in order to secure the stability of the primer, a desiccant such as synthetic zeolite which is inactive against isocyanate groups can be blended.

The pretreatment composition and the primer of the present invention as described above can be mixed and adjusted using various known apparatuses which can sufficiently mix the respective components. It is preferred to use

As a pretreatment method, the adherend surface of the adherend is
Preferably, the pretreatment composition of the present invention is applied to the surface of the adherend after sanding with sandpaper or the like to improve the conformity of the non-adhesive surface and the pretreatment composition present on the adherend surface.
Apply 10 to 100 g / m ² , brush, etc., and dry. Next, after irradiation with ultraviolet rays, a primer is applied, an adhesive is applied on the primer, and the adherend is adhered.

The ultraviolet irradiation performed in the present invention can use an apparatus known per se. For example, it is performed using a mercury lamp (low pressure, medium pressure, high pressure, ultra high pressure), a metal halide lamp, a chemical lamp, or the like. The irradiation amount of the ultraviolet light to the adherend is usually 0.1 J / cm ² or more, particularly 0.5 J / cm ^2.
It is preferably set to 10 to 10 J / cm ² .

In the present invention, the surface to be coated is treated with the pretreatment composition, dried, irradiated with ultraviolet rays, and then coated with a primer. This coating can be performed by a known method. For example, there is a method in which the primer of the present invention is applied by spraying or the like, and then left to dry. The amount of the primer applied to the adherend depends on the type of the photopolymerization initiator and the fluorescent dye, but is usually 10 g / m ² or more.
Preferably, it is about 10 to 100 g / m ² .

The adherend whose surface has been pretreated with the pretreatment composition of the present invention and the primer described in detail above is applied to the adherend using a urethane-based, epoxy-based, acrylic-based adhesive or the like. It is possible to adhere by a method known per se. The adhesive used in the present invention is preferably an adhesive that can be used for direct glazing.

The material adhered to the adherend via the adhesive may be the same as the adherend, but in many cases, a material which is easily adhered to a urethane-based adhesive such as rubber or plastic is used. .

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but it should not be construed that the present invention is limited thereto.

Using the following adherend, pretreatment composition, primer and adhesive sealant for urethane-based direct glazing, the following test piece for peel test was prepared, and the following peel test was carried out. The adhesive force when using the pretreatment composition of the invention, the primer, and the conventional primer alone was compared. (1) The adherend used was a GF-reinforced polypropylene sheet (3 mm thick) containing 40% by weight of glass fiber.
And used as 10.0 cm x 2.5 cm square.

(2) Test pieces were prepared using the pretreatment compositions and primers shown in Table 2. Two types of pretreatment compositions were prepared: a pretreatment composition containing a photopolymerization initiator and a solvent, and a pretreatment composition containing a photopolymerization initiator, a fluorescent dye, and a solvent. As the photopolymerization initiator, a 10% isopropanol solution of Irgacure 651 manufactured by Ciba Geigy was used.
As a fluorescent dye, Kayalite FG (oxazole compound) manufactured by Nippon Kayaku Co., Ltd. was added in the composition shown in Table 2.

The isocyanate used is Desmodur RFE manufactured by Bayer AG, the solvent is ethyl acetate, the carbon is thermal carbon manufactured by Asahi Thermal, the drying agent is synthetic zeolite, the catalyst is a tin-based catalyst, and the urethane resin is D
Pandex manufactured by IC Company was blended and adjusted. These compounds were mixed in a ball mill for 6 to 24 hours to obtain a pretreatment composition and a primer, respectively.

1) When a fluorescent dye was added, the optimum addition amount (% by weight) based on the total amount of the pretreatment composition or primer was examined. Oxazole-based Kayalite FG was used as the fluorescent dye. Table 1 shows the results.

Table 1—Amount of fluorescent dye added 0 1 2 3 4 (weight %) 沈 殿 Presence or absence of precipitation No No No Yes Yes ─────── ──────────────────────────

From Table 1, it was found that when the amount of addition was 3 to 4% by weight or more, Kayalite FG was not dissolved and precipitation was observed. Therefore, in the examples of the present invention, 0.01 to 2% by weight was used. 2) The bonding method is divided according to the addition of the fluorescent dye, and the first bonding method of adding the fluorescent dye to the pretreatment composition used before the ultraviolet irradiation is added to the pre-addition method and the primer used after the ultraviolet irradiation. Using the second bonding method as a post-addition method, bonding was performed in the following procedure to prepare a cohesive failure test specimen. First, the surface of the adherend is # 180-250.
Was sanded using a sandpaper to remove the non-adhesive layer formed on the adherend surface. Next, the adherend surface of the adherend was treated with the pretreatment composition and dried to evaporate the solvent. Thereafter, the surface of the adherend was irradiated with ultraviolet rays at 1 J / cm ² using an ultraviolet lamp. After irradiation with ultraviolet light, a primer was applied and dried again at room temperature. Thereafter, the adherend was bonded to the urethane rubber using a urethane-based adhesive sealing agent for direct glazing and cured.

3) With respect to the test piece thus obtained,
The cohesive failure test was performed under the following two conditions. For the initial cohesive failure, the test piece prepared as described above was placed at 20 ° C. and a standard humidity state of 65% for 7 days, peeled manually, and the residual ratio on the adhered surface of the adherend was measured. The water-resistant cohesive failure is performed by placing the test piece prepared as described above at 20 ° C. and a standard humidity of 65% for 7 days, then immersing the test piece in warm water at 40 ° C. for 10 days, peeling by hand, and bonding the adherend to the adherend. Was measured.

Example 1 (1) Comparison of Adhesive Strength When Using Post Addition Method The test pieces of Examples 1 to 3 of the present invention used the pretreatment composition and the primer shown in Table 2, respectively. Were prepared as described above, and a cohesive failure test was performed. The test piece of Comparative Example 1 used the pretreatment composition primer shown in Table 2,
Other conditions were prepared as described above, and a cohesive failure test was performed. The test piece of Comparative Example 2 was prepared by using the pretreatment composition and the primer shown in Table 2, not irradiating ultraviolet rays, and preparing other conditions as described above, and performing a cohesive failure test. Table 2 shows the results. Comparing the results shown in Table 2 with the initial adhesive strength, Examples 1 to 3 of the present invention to which a fluorescent dye was added.
Showed good initial adhesive strength. Looking at the difference in adhesive strength due to the added fluorescent dye, it is clear from the results of the cohesive failure test of Invention Examples 1 to 3 that Kayalite FG
> Kayalite B> Kayalite OS, the adhesive strength decreased in this order. On the other hand, in Comparative Example 1 prepared using the pretreatment composition and the primer containing no fluorescent dye, both the residual ratio in the initial bonding and the residual ratio in the water-resistant bonding were 0%. Also, in Comparative Example 2 which was prepared using a primer to which a fluorescent dye was added and without irradiating ultraviolet rays, the residual ratio in initial bonding and the residual ratio in water-resistant bonding were both 0.
%, Indicating that without UV irradiation, the adhesion was not strengthened even when the fluorescent dye was added to the primer.

(2) Comparison of adhesive strength depending on the amount of fluorescent dye added It was found that the initial adhesive strength was increased by ultraviolet irradiation and application of a primer to which the fluorescent dye was added. Among them, Kayalite FG, which had the highest residual ratio in the initial bonding, was used to change the amount added, and the change in bonding strength was examined. The amount of Kayalite FG added to the isocyanate component of the primer in Examples 1 and 5 was 2 parts by weight, and the amount of Kayalite FG in Examples 4 and 6 was 10 parts by weight. The test pieces of Comparative Example 3 were prepared using the pretreatment composition primers shown in Table 3, and the other conditions were as described above. The test piece of Comparative Example 4 was prepared using the pretreatment composition and the primer shown in Table 3, and the other conditions were as described above. Table 3 shows the results. In Table 3, as is clear from the results of the cohesive failure test of Invention Examples 1 and 4, the initial adhesive strength increased as the amount of the fluorescent dye added increased, but the water-resistant adhesive strength showed almost no change. It has been shown.

(3) Effect of Compounding Carbon Next, it was examined how the water-resistant adhesive strength changes when carbon is added to a primer containing a fluorescent dye. Table 3 shows the results. From the results of Inventive Examples 5 and 6 shown in Table 3, the initial adhesive strength was slightly higher in Inventive Example 5 in which the amount of the fluorescent dye added was small, but the residual ratio in water-resistant adhesion was 75% in each case. The strength was remarkably strengthened as described above, and it was shown that the addition of carbon increased the water-resistant adhesive strength. In addition, in each of Inventive Example 1 and Inventive Example 5 shown in Table 3, the amount of the fluorescent dye added was small, but when these were compared, not only the water-resistant adhesive strength but also the initial adhesive strength were enhanced by the compounding of carbon. It was shown that. Further, in Comparative Example 4 in which ultraviolet rays were not irradiated even when carbon was blended, the residual ratios in the initial adhesion and the water-resistant adhesion were both 0%. The residual ratio of Comparative Example 3, which was irradiated with ultraviolet rays and blended with carbon, was 45% in the initial adhesion, and 5% in the water resistance.
It was clarified that the combination of carbon and ultraviolet irradiation greatly improved the initial adhesive strength, and that the fluorescent dye was indispensable for improving the water-resistant adhesive strength.

Example 2 Difference in Enhancement of Adhesive Strength between Pre-Addition Method in Which Fluorescent Dye was Added to Pretreatment Composition Used Before UV Irradiation and Post-Addition Method Added to Primer Used After UV Irradiation It was investigated. The amount of the fluorescent dye added was 0.2% by weight in the pre-addition method and 0.2% by weight in the post-addition method. Table 4 shows the results. (1) Effect in the pre-addition method As shown in Table 4, the present invention example 1 by the post-addition method
Comparing Example 7 of the present invention with the pre-addition method, the residual ratio in the initial adhesion was 98% in the pre-addition method, and 80% in the post-addition method, and was higher in the case of the pre-addition method. However, the residual ratio in water-resistant bonding was 0% in all cases.
Met. When carbon was used in combination with the pre-addition method showing a high residual ratio in the initial bonding, the residual ratio in the initial bonding did not change, and the residual ratio in the water-resistant bonding increased to 30%. (2) Effect in post addition method However, as shown in Table 3, when the post addition method and carbon were used in combination, the residual ratio in water-resistant adhesion was 75%.
Or, it was improved to 95%, indicating that the combined effect of the post-addition method and carbon was larger.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

When a pretreatment composition containing a photopolymerization initiator having no hydroxyl group and a fluorescent dye is applied, and a primer containing an isocyanate compound is used after irradiation with ultraviolet rays,
And, when applying a pretreatment composition containing a photopolymerization initiator having no hydroxyl group and using a primer containing a fluorescent dye and an isocyanate compound after irradiating ultraviolet rays, the fluorescent dye is contained in these compositions. The initial adhesive strength was improved as compared with the case without the case. Also, the combined use of a fluorescent dye and carbon greatly improved the water-resistant adhesive strength. Further, when a fluorescent dye was blended, the effect was greater when the post-addition method was adopted than in the pre-addition method. By using the pretreatment method for bonding according to the present invention, it has become possible to strongly bond a polyolefin such as polypropylene, which is a poorly adhesive material, to a urethane rubber.

Continuation of the front page (56) References JP-A-4-185654 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 7/04

Claims (3)

(57) [Claims] 1. A pretreatment composition containing a photopolymerization initiator having no hydroxyl group and a fluorescent dye is adhered to the adherend surface of the adherend, and then irradiated with ultraviolet rays, and then a primer containing an isocyanate component is applied. A pretreatment method for bonding an adherend. 2. After adhering a pretreatment composition containing a photopolymerization initiator having no hydroxyl group to the adherend surface of the adherend, irradiating it with ultraviolet light, and then applying a primer containing a fluorescent dye and an isocyanate component A pretreatment method for bonding an adherend. 3. The pretreatment composition according to claim 1, wherein the content of the photopolymerization initiator having no hydroxyl group is 0.5 to 50% by weight, and the content of the fluorescent dye is 0.01 to 2%. The pretreatment method for bonding an adherend according to claim 1 or 2, wherein the primer is used.