JP3255772B2 - 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 adhesion to metals and other plastics due to low polarity. . In particular, molding and use alone, for example, composite structural materials such as seat cushion covers and bumpers as automotive parts,
When used by bonding to plastic, metal, or the like, the problem of poor adhesion is a problem. Adhesion is an interfacial phenomenon,
It is essential that the surface of the adherend be wetted 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 adhered with 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 bonding polyolefin,
Since wet surface treatment such as acid treatment results in extremely insufficient surface oxidation, various dry treatments such as plasma and ultraviolet (U)
V) irradiation or the like has been performed to oxidize the surface, and to impart a polar group to the surface so that van der Waals force or hydrogen bonding acts. However, these treatments alone are not enough to oxidize the polyolefin surface,
Since polar groups or functional groups are not sufficiently formed, the adhesive strength may be insufficient, and further improvement in adhesiveness has been desired. We have already filed Japanese Patent Application No. 4-283109.
No. 4,972,838, filed an application for 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. 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.

[0004]

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 applies a pretreatment composition containing a photopolymerization initiator and a pigment to an adherend surface, and after irradiation with ultraviolet light, applies a primer composition containing a polyisocyanate compound to bond the poorly-adhesive material. Provide a method to improve the performance. That is, in the present invention, a pigment which was not used in the pre-treatment composition of the hard-to-adhere material is uniformly dispersed in the pre-treatment composition to form a sea-island structure and the coating film is tough. The purpose is to provide a method.

That is, according to the present invention, a pretreatment composition containing a photopolymerization initiator having no hydroxyl group and a pigment is applied to the adherend surface of the adherend, followed by irradiating ultraviolet rays and then containing a polyisocyanate compound. A pretreatment method for bonding an adherend, characterized by applying a primer. The pretreatment method, the pretreatment composition containing a pigment and a photopolymerization initiator having no hydroxyl group that is cleaved by light to generate a radical, the adherend surface of the adherend, preferably sanded with sandpaper Characterized in that it is attached to Here, the photopolymerization initiator having no hydroxyl group used may be a photodecomposition type or a photoexcitation type photopolymerization initiator, and the content thereof is 0.5 to 50% by weight. Is preferred. Further, the pretreatment method is characterized in that a pretreatment composition containing the photopolymerization initiator and the pigment is applied before irradiation with ultraviolet rays. The pigment preferably has good wettability with the urethane resin blended in the primer. It is preferable that the composition is uniformly dispersed in the pretreatment composition, and the specific content is preferably in the range of 1 to 10% by weight.
Further, in the pretreatment method of the present invention, by adding the pigment to the pretreatment composition, the structure of the layer formed on the adherend surface of the pretreated adherend is changed to a liquid component of sea and a pigment. The island is characterized by a strong island structure.

Hereinafter, the present invention will be described in detail.

The adherend using the pretreatment method of the present invention is preferably a polyolefin, specifically, a polyethylene resin, a polypropylene resin, a poly-1-butene resin, a poly-4-methyl-1-pentene resin, or the like.

[0008] 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. As a photodegradable 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.

[0010] The photo-excitation type photopolymerization initiators include

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.

[0012] 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 capable of dissolving 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 blended 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. 1-20% by weight is preferred.

The pretreatment composition of the present invention may contain a pigment having a high affinity for the urethane resin or the like blended in the primer. The pigment refers to an inorganic or organic fine particle solid that is insoluble in water or oil, and includes compounds such as metal oxides, metal sulfides, and metal phosphates. It is preferable that the pigment added here has good compatibility with the urethane resin and the like and has good wettability. In particular,
Preference is given to titanium oxide, silica, metal phosphates, in particular titanium oxide or aluminum polyphosphate. These metal compounds may be further subjected to a surface treatment such as zinc and silica to impart hydrophilicity.

The amount of the pigment which can be added to the pretreatment composition of the present invention is usually such that the adhesive strength is enhanced and the pigment is uniformly dispersed when the entire pretreatment composition is 100% by weight. Is in the range of 1 to 10% by weight. Particularly, 2 to 5% by weight is preferable.

The composition for pretreatment is preferably prepared by mill-mixing with a pigment, a photopolymerization initiator and a solvent to be added for 6 to 24 hours, and then dispersed.

The primer used in the pretreatment method of the present invention contains an isocyanate component. Here, the isocyanate component is 4,4′-diphenylmethane diisocyanate (MDI), tolylene diisocyanate (T
DI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), hydrogenated (hydrogenated) MDI, hydrogenated TDI, hydrogenated XDI, isophorone diisocyanate (IPDI), aromatic aliphatic polyisocyanate, aromatic polyisocyanate , Triphenylmethane triisocyanate, tris-p-isocyanate phenyl thiophosphate and the like, and a mixture thereof in an appropriate combination. In particular, a combination of MDI, tris-p-isocyanate phenylthiophosphate and aromatic isocyanate is preferable.

The primer of the present invention may 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 00 to 1000 parts by weight is preferable.

Further, it is possible to mix carbon in the primer of the present invention.
The water-resistant adhesiveness is improved. However, if the amount is too large, the dispersion of the carbon particles in the primer becomes worse, and clogging or the like may occur in the production machine, which may cause a failure. On the other hand, it is preferably about 50 to 200 parts by weight.

Various catalysts can be added to the primer used in the present invention as optional components. 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 component.

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 above-mentioned pretreatment composition and primer of the present invention can be mixed and adjusted using various known devices capable of sufficiently mixing the respective components, such as a ball mill. It is preferred to use

In the pretreatment method, the surface of the adherend is preferably sanded with sandpaper or the like to improve the conformity of the non-adhered surface of the adherend, and then the pretreatment composition of the present invention is added in an amount of 10 to 100 g / day. An amount of m ² is applied to the surface of the adherend by a method such as coating or brushing, and dried. Thereafter, ultraviolet rays are irradiated, a primer containing an isocyanate compound is applied, and an adhesive is applied on the primer to adhere the adherend.

The ultraviolet irradiation can be performed using a device 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 amount of UV radiation to the surface
Usually, 0.1 J / cm ² or more, especially 0.5 to 10 J / c
m ² is preferable.

In the present invention, the pretreatment composition is applied to the surface to be applied, dried, irradiated with ultraviolet rays, and then a primer is applied. This application 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 coating amount of the primer to an adherend surface, depending on the type of pretreatment composition used, typically 10 g / m ² or more, preferably about 10 to 100 g / m ² is preferred.

The adherend whose surface has been pretreated by using the pretreatment composition and the primer of the present invention described in detail above is treated with a urethane-based, epoxy-based, or acrylic-based adhesive. It is possible to adhere by a method known per se. A urethane-based adhesive sealing material used for direct glazing is preferred.

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. .

[0030]

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 sealing agent for direct glazing, the following test specimen for peel test was prepared, and the following peel test was carried out. Of the pretreatment composition and the primer were compared with those of a conventional primer alone. (1) The adherend used in this example was a 10.0 cm × 2.5 cm square from a GF-reinforced polypropylene sheet (3 mm thick) containing 40% by weight of glass fiber.

(2) The pretreatment composition and the primer of the present invention were formulated according to the formulations shown in Tables 2 and 3 to prepare test pieces. The photopolymerization initiator was a 10% ethyl acetate solution of Irgacure 651 manufactured by Ciba-Geigy, and the pigment was K-WH, a surface-treated aluminum dihydrogen polyphosphate manufactured by Teika.
ITE or titanium oxide manufactured by Ishihara Sangyo Co., Ltd. was used.

As the isocyanate, Desmodur RFE manufactured by Bayer AG, the solvent is ethyl acetate, the carbon is thermal carbon manufactured by Asahi Thermal, the desiccant is a synthetic zeolite, the catalyst is a tin-based catalyst, and the urethane resin is D
Pantex manufactured by IC Company was blended and adjusted. All of the pigments used here are compounds that are hardly soluble in ethyl acetate used as a solvent.

1) In the case of adding a pigment, the optimum amount (% by weight) of the total amount of the pretreatment composition was examined. K-WHITE was used as a pigment. Table 1 shows the results.

Table 1—Amount of Pigment Added 0 0.5 15 10 15 (% By weight) 程度 Degree of dispersion Uniform Uniform Uniform Uniform Uniform Nonuniform ───有無 Presence or absence of precipitation No No No No No Yes ─────────── ──────────────────────

From Table 1, it can be seen that when the added amount exceeds 10% by weight, uniform dispersion of all the pigments becomes impossible, and precipitation is observed. Therefore, in the following examples of the present invention, 5% by weight was used. 2) Regarding the bonding method, a test piece for a cohesive failure test was prepared in the following procedure. First, the surface of the adherend is # 180 ~
The surface of the GF-reinforced polypropylene was sanded using a sandpaper of No. 250 to remove the non-adhered layer formed on the adherend surface. Next, the adherend surface of the adherend was wiped with the pretreatment composition and dried to evaporate the solvent. Then, ultraviolet rays were applied to the surface of the adherend with an ultraviolet lamp at 1 J / cm ^2.
Irradiated. 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 polyurethane adhesive sealing agent for direct glazing and cured. 3) The cohesive failure test was performed on the test piece thus obtained 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, manually peeled off, and the residual ratio on the bonded 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 state 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. The residual ratio on the surface was measured.

(Examples) (1) Comparison of Adhesive Strength Due to Differences in Pigment to be Added The test pieces of Examples 1 and 2 of the present invention were 5% by weight of surface-treated aluminum polyphosphate, K-WHITE manufactured by Teika Co., Ltd.
A test piece was prepared as described above by adjusting the added pretreatment composition and the pretreatment composition to which 5% by weight of titanium oxide was added, and subjected to a cohesive failure test. The test piece of Comparative Example 1
Using a pretreatment composition containing no pigment shown in Table 2, a test piece was prepared under the other conditions as described above, and a cohesive failure test was performed. The test piece of Comparative Example 2 used the pretreatment composition shown in Table 2 containing no titanium oxide and a solvent without containing a photopolymerization initiator, and other conditions were used to prepare a test piece as described above. The test was performed. Table 2 shows the results.

[0038]

As shown in Table 2, when compared with the initial adhesive strength, in Examples 1 and 2 of the present invention to which K-WHITE or titanium oxide was added, the residual ratio showed a high value of 95% or more. In Comparative Example 1 including a photopolymerization initiator and no pigment, and Comparative Example 3 including no titanium oxide and no photopolymerization initiator, the initial adhesion was 0% and the adhesive strength was extremely small. In each of the inventive examples 1 and 2 and the comparative examples 1 and 2, the residual ratio was 0% in the water-resistant adhesive, and the water-resistant adhesive strength was not improved only by adding the pigment. (2) Comparison of water-resistant adhesive strength when pigment and carbon were used in combination The same pretreatment compositions as those used in Examples 1 and 2 of the present invention were prepared, and carbon was blended into a primer. A test piece was prepared under the above-described conditions shown in FIG. In Comparative Examples, carbon was blended in the primer, Comparative Example 3 using the pretreatment composition having the formulation shown in Table 3 containing the primer, the photopolymerization initiator, and the solvent, and the photopolymerization initiator, titanium oxide A test piece was prepared in Comparative Example 4 using a pretreatment composition having the formulation shown in Table 3 containing a solvent and a solvent. Table 3 shows the results.

[0040]

As shown in Table 3, when compared with the initial adhesive strength, in Examples 3 and 4 of the present invention to which K-WHITE or titanium oxide was added, the residual ratio showed a high value of 95% or more. Even when a pretreatment composition containing a photopolymerization initiator and containing no pigment was used, when a primer containing carbon was used, the initial adhesion was 45 as shown in the results of Comparative Example 3.
%, But the water resistant adhesion was not improved at a low value of 5%. In Comparative Example 4, the values of both the initial adhesion and the water-resistant adhesion were as small as 2% and 3%. In Inventive Examples 3 and 4, water-resistant adhesion was enhanced by the addition of carbon. However, the results of Comparative Examples 3 and 4 show that the addition of only carbon does not improve the water-resistant adhesiveness. For this improvement, it is necessary to use a photopolymerization initiator, a pigment and carbon in combination. It became clear that it was.

[0042]

When a pretreatment composition containing a photopolymerization initiator having no hydroxyl group and a pigment and a primer containing a polyisocyanate compound are used, the pretreatment composition and a polyisocyanate compound containing no pigment are used. The initial adhesive strength was greatly improved as compared with the case where the primer containing the primer was used. Further, by adding carbon to the primer, the water-resistant adhesive strength was also remarkably improved. 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 (1)

(57) [Claims] 1. A photopolymerization initiator having no hydroxyl group on the surface to be adhered of 0.5 to 50% by weight and a pigment of 1 to 10% by weight.
A method for pretreating an adherend, comprising applying a pretreatment composition containing the composition, irradiating the composition with ultraviolet light, and then applying a primer composition containing a polyisocyanate compound.