JPS6133874B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a powdered high-frequency adhesive made of vinylidene chloride copolymer. More specifically, it relates to a powdered high-frequency adhesive made of a vinylidene chloride copolymer that has a specific monomer composition and has a practical high-frequency adhesive strength that easily wets metals, glass, wood, fibrous materials, plastics, etc. It is. Conventionally, there have been film-like high-frequency adhesives made of soft vinyl chloride resin film or low-melting point polyamide film, and film-like high-frequency adhesives made from vinyl chloride resin latex or vinylidene chloride copolymer latex. Recently, high-frequency adhesives made of vinyl chloride resin powder and low-melting polyamide resin powder have been developed, but they contain plasticizers, have too low dielectric loss, and have too low total wetting characteristics to be practical. There is no powdered high frequency adhesive that has the same high frequency adhesive strength. High-frequency adhesives have attracted particular attention in recent years because they have the following three major advantages. It can be stored in film or powder form before adhesion and is easy to handle. At the time of adhesion, bonding can be achieved by simply applying a high frequency voltage for a short time, and in principle, the adhesive force can be easily controlled arbitrarily by adjusting the application time of the high frequency voltage, the contact pressure, and the contact pressure temperature. The high frequency bonding process is easy to automate and can easily be inlined or roboticized into various continuous assembly processes. With recent advances in miniaturization, precision, and reliability of high-frequency generators and their electronic control mechanisms, high-frequency bonding machines and welders have become smaller and cheaper, and are being incorporated in-line into various continuous bonding processes. For example, high-frequency bonding machines and welders are extremely effective in the process of continuously manufacturing adhesive structures that are produced in small quantities in large quantities at high speeds, or in processes that continuously produce adhesive structures in large quantities in small quantities at high speeds. Examples of specific products for which such high-frequency adhesive machines are effective are: (1) Industrial textile materials (sewing tents and sheets) (2) Synthetic and laminated materials (3) Unit furniture (4) Interiors (Automobile interior materials, ship interior materials, aircraft interior materials) For example, there are complex curved stitches for ceiling materials, wall materials, carpets, seats, doors, etc. Materials suitable for high-frequency bonding machines are those that essentially generate heat due to dielectricity in the applied high-frequency electric field.
It must be a material that melts or softens, crosslinks and hardens. In order to generate this dielectric heat generation, dielectric loss is important in correspondence with the applied high frequency. On the other hand, it is common knowledge when using adhesives that if the wetting with the adhered material is not sufficient, peeling will occur at the adhesive interface and the desired adhesive force will not be obtained. As materials that generate high-frequency dielectric heat generation, examples of the former include polyvinyl chloride resin, polyvinylidene chloride resin, and polyamide resin, and examples of the latter include phenol, urea, resorcinol, and melamine resin. The former high-frequency dielectric heating material is generally used in the form of a film or a latex-coated film, and the latter high-frequency dielectric heating material is generally used in the form of an aqueous solution, an alcoholic solution, or a suspension in water or an alcoholic medium. It is generally used as a liquid. Although the thermosetting high-frequency adhesive has excellent adhesive strength, it essentially has four drawbacks. (1) It is a wet type containing a large amount of water or alcohol, making it difficult to handle and store. (2) A drying process is required to evaporate water or alcohol, and a large amount of drying energy is required. Furthermore, the drying speed is slow and productivity is lacking. (3) Systems that use alcohol have faster drying speeds than water systems, but they have drawbacks in terms of fire, environmental pollution, and health and safety. (4) Since it is a wet system, it is difficult to incorporate it as an in-line system. Thermoplastic high frequency adhesives are superior to adhesives because they are essentially dry, but they have four drawbacks: (1) It is difficult to position the film-like adhesive and the material to be adhered, and there is a problem that the positioning may shift with a slight external force. (2) The film must be cut depending on the size of the material to be adhered, and even if scraps of film are produced, they cannot be reused and are lost. (3) The film insertion process is difficult to automate, making it difficult to incorporate it into an in-line system. (4) Nylon film has poor wetting characteristics, and polyvinyl chloride resin and polyvinylidene chloride resin are easily altered in the film forming process, and plasticizers, etc. must be used, so there is a limit to how well they can improve wetting with the bonded material. In some cases, adhesive interface peeling may occur. A new high-frequency adhesive that eliminates the disadvantages of thermoplastic high-frequency adhesives such as positioning, loss, and wettability with adhered materials, and does not have the disadvantages of wet-type thermosetting high-frequency adhesives. was required. The following four basic performance requirements are listed below. It's dry. There is no loss and it can be reused. It is an adhesive that can be easily integrated into in-line systems. Wetting with the adhered material can be easily controlled. As a result of intensive research in response to the above requirements, the present inventors were able to provide a powdered high-frequency adhesive made of a vinylidene chloride copolymer that satisfies the four basic required performances. That is, according to the present invention, vinylidene chloride component (A) of 64 mol% or more and 93 mol% or less and 7 mol% of one or more monomers copolymerizable with component (A).
Above, 36 mol% or less monomer component (B) and 0 mol% or more and 10 mol% or less monomer component (C A spherical powder high-frequency adhesive having a particle diameter of 1 μm or more and 500 μm or less is provided, which is a crystalline vinylidene chloride copolymer consisting of the following: Specific requirements of the invention and examples thereof will be shown below, but the invention is not limited to the content thereof. Known suspension polymerization methods, solution polymerization methods, and mass polymerization methods can be adopted as methods for producing the adhesive of the present invention. However, in the suspension polymerization method, spherical particles are obtained as an aqueous dispersion, and the particle size is small. This is preferable because it can be arranged within a narrow range. In the above polymerization method, known organic peroxides, such as lauroyl peroxide and diisopropyl peroxydicarbonate, and azobis compounds, such as azobisisobutyronitrile and azobisdimethylvaleronitrile, are used as oil-soluble radical initiators. Ru. Monomer component (B) copolymerizable with vinylidene chloride
As such, α-monosubstituted unsaturated ethylenic monomers and unsaturated carboxylic acid ester monomers can be used. Preferably a mixture of one or more selected from vinyl chloride, vinyl acetate, vinyl methyl ether, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, acrylonitrile, methacrylonitrile, etc. can be used. More preferred are vinyl chloride, vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, ethylhexyl acrylate, and acrylonitrile because they are inexpensive. Vinylidene chloride (A) and/or monomer (B)
As the functional monomer (C) that can be copolymerized with, monomers selected from unsaturated carboxylic acids, dicarboxylic acids, α-alkyl-substituted unsaturated carboxylic acids, amides of these acids, hydroxyalkyl esters, glycidyl esters, or mixtures thereof, etc. is used. Preferably acrylic acid, methacrylic acid,
Itaconic acid, maleic acid, maleic anhydride, fumaric acid, acrylamide, methacrylic acid amide, hydroxyethyl acrylate, glycidyl methacrylate are used. More preferably acrylic acid, methacrylic acid, acrylamide,
Methacrylic acid amide, itaconic acid, hydroxyethyl acrylate, and glycidyl methacrylate are good because they are easily available industrially. Vinylidene chloride(A)
The composition of component (B) component monomer and functional monomer (C) component is 64 mol% or more of vinylidene chloride, 93
It is preferable that the component monomer (B) is 7 mol % or more and 36 mol % or less, and the (C) component monomer is 0 mol % or more and 10 mol % or less. Preferably vinylidene chloride 70 mol% or more and 90 mol% or less, component (B) monomer 10 mol%
or more, 30 mol% or less, (C) component monomer 0.1 mol%
The content is 8 mol% or less. More preferably, the vinylidene chloride content is 80 mol% or more and 90 mol% or less, the (B) component monomer is 10 mol% or more and 20 mol% or less, and the (C) component monomer is 0.5 mol% or more and 5 mol% or less. When the vinylidene halide is 64 mol% to 93 mol%, the copolymer is crystalline and crystallization occurs after bonding with high frequency, which improves the tensile strength of the copolymer itself, which is preferable. Among the copolymer composition ranges of the present invention, a certain composition provides such a tensile strength that cohesive failure does not occur and the adherend breaks. If vinylidene chloride is less than 64 mole percent, the copolymer is amorphous. If the vinylidene chloride content exceeds 93 mol%, high frequency dielectric heat generation decreases, and the melting temperature of the copolymer becomes too high, and the copolymer is not sufficiently melted and softened, making it impossible to obtain practical adhesive strength, which is not preferable. Introduction of the functional monomer component (C) is preferable in order to further improve adhesive strength. The presence of a functional monomer component is preferred for bonding structural materials, such as bonding plywood, laminated wood, metals to metals or metals to other materials, such as plywood, paperboard, hardboard, etc. For non-structural adhesion of nonwoven fabrics, cloth interlinings, etc., the amount of the functional monomer component may be small. If the content of the functional monomer exceeds 10 mol %, the water absorption of the copolymer becomes high, and when used as an adhesive, the water resistance decreases, which is not preferable. When component (C) is introduced, the adhesive force increases with the amount introduced, reaches a maximum, and then decreases again. Even if more than 10 mol % of the copolymer is introduced, the adhesive strength will not increase even if it is lower than that of the non-incorporated copolymer, which is not preferable. Also, functional monomers
By introducing 0.05 mol% or more, the effect of introducing the functional monomer (improvement of wettability and interfacial adhesive strength) is manifested. As a method for analyzing component (C), pyrolysis gas chromatography conductivity measurement is simple and has good analytical accuracy. The accuracy of analysis using these methods is up to 1×10 ⁻⁴ mol/g for the copolymer. Spherical particles with a particle size of 1 μm or more and 500 μm or less are good because they are easy to handle as a powder.
The thickness is preferably 10μ or more and 400μ or less, more preferably 100μ or more and 300μ or less. When the above particle diameter range is expressed using a JIS standard sieve, it is 32 mesh passes, preferably 42 mesh passes and 846 mesh units, and more preferably 48 mesh passes and 170 mesh units. Particles smaller than 1μ are difficult to handle as powder and have the disadvantage of causing secondary agglomeration. Particles larger than 500μ have the disadvantage that the adhesive spreads uniformly on the material to be adhered, causing non-uniform adhesion. The frequency of high-frequency adhesive machines is only allowed as specified by the Radio Law, but above 10MHz,
100MHz or less is preferable. If the frequency is below 10MHz, the adhesive will have difficulty in withstanding voltage, and sparks may occur during bonding. At frequencies above 100 MHz, high-output vacuum tubes are not manufactured industrially, and the adhesive locally generates heat, which is undesirable. Currently, frequencies of 13.56, 27.12, and 40.46 MHz can be used for high-frequency adhesive machines permitted by the Radio Law, and high-frequency power supplies of all frequencies can be used for the adhesive of the present invention. In order for the high frequency dielectric heating value to be sufficient to melt and/or soften the adhesive,
Dielectric loss at 27.12MHz and 20°C should be 0.02 or more. It is preferably 0.04 or more, more preferably 0.05 or more. If the dielectric loss is less than 0.02, the amount of high-frequency dielectric heat generation will be insufficient, and the adhesive will not be sufficiently melted and/or softened, making it impossible to obtain practical adhesive strength, which is not preferable. In structural adhesives, wetting of the adhesive onto the surface of the adhered material plays an important role. Poor wetting causes peeling from the interface between the adhesive and the adhered material, resulting in adhesive strength that is significantly lower than the strength of the adhesive itself. It is very difficult to accurately obtain interfacial wetting property values. The present inventors adopted the following evaluation method to quantify wettability practically. Total wetting property value A powder adhesive that does not contain functional monomer components is applied uniformly to an aluminum plate at 150g/ ^m2 , and the aluminum plate is placed on top of it and bonded for 30 seconds using a 40MHz, 1kw (manufactured by Pearl Industries) high frequency adhesive machine. The shear adhesion strength of a 2.5 cm x 2.5 cm sample as a bonded surface subjected to high frequency bonding under a pressure of 5 Kg/cm ² is measured at 20° C. using an Instron tensile tester at a tensile speed of 10 cm/min. The adhesive force is RKg/cm ² . Using powdered non-adhesives made with varying amounts of functional monomer components, aluminum plate samples were made that were bonded under the same conditions as above, and the adhesive strength was measured under the same conditions as above. The adhesive strength is SKg/cm ² . The various functional monomer components are plotted on the horizontal axis.
Plot the dielectric loss at 27MHz and plot the adhesion force on the vertical axis. Total wetting characteristic value = ΔS / ΔL _S / ΔR / ΔL _R ΔS: Difference in adhesive strength of adhesives containing functional monomers ΔL _S : Difference in dielectric loss of adhesives containing functional monomers ΔR: Functionality Difference in adhesive strength between adhesives containing no monomer ΔL _R : Difference in dielectric loss between adhesives containing no functional monomer When the total wetting characteristic value is less than 1.0, the effect of the functional monomer component is substantially reduced. This is undesirable because interfacial peeling occurs. Therefore, the total wetting characteristic value defined above must be greater than or equal to 1.0. The larger the total wetting characteristic value is, the better, but a value exceeding 200 is not practical because the surface of the adhered material must be kept ideally free from contamination. The present invention will be described in detail below using specific examples, but the present invention is not limited only to the examples. Example 1 A crystalline vinylidene chloride copolymer with a melting point of 142°C and a heat of fusion of 2.0 cal/g by DSC (manufactured by PerkinElmer), consisting of 75.5 mol% vinylidene chloride and 24.5 mol% vinyl chloride, and diisopropyl peroxydicarbonate. A spherical powder high-frequency adhesive prepared by suspension polymerization using a radical initiator and passing through a JIS standard sieve with a 60-mesh pass and a 170-mesh diameter was applied to a paperboard (Jujo Paper Co., Ltd., Jupylite) with a particle diameter of 80 g/ ^m2. Table 1 shows the adhesion strength and dielectric loss when the adhesive was coated as described above and high frequency bonded using a 40 MHz, 1 kW high frequency bonding machine (Pearl Industries) for 15 seconds under a pressure of 6 kg/cm ² . Practical adhesive strength using this test method is 2Kg/
^cm2 .

[Table] Example 2 Vinylidene chloride 90 mol%, methyl acrylate 10
It is a crystalline vinylidene chloride copolymer with a melting point of 143°C measured by DSC (manufactured by PerkinElmer), consisting of 1 mol% of acrylic acid and 1 mol% of acrylic acid, prepared by suspension polymerization using azobisisobutyronitrile as a radical initiator. JIS as particle size range
A spherical powder high-frequency adhesive with a standard sieve pass of 60 meshes and a mesh size of 170 meshes was obtained. For comparison, a copolymer obtained by polymerization under the same conditions as in the example containing no acrylic acid was a crystalline vinylidene chloride copolymer with a melting point of 145°C. Table 2 shows the particle size, dielectric loss, and total wetting characteristic values for each. This adhesive was applied to No. 5 chemical filter paper, and the same filter paper was placed on top of it and high frequency adhesion was attempted under the same conditions as in Example 1.
Shown in 2.

[Table] Comparative Example 1 A crystalline vinylidene chloride copolymer with a melting point of 190°C as determined by DSC (manufactured by PerkinElmer), consisting of 93.5 mol% vinylidene chloride (VDC) and 6.5 mol% vinyl chloride (VC), A spherical high-frequency adhesive made of a copolymer suspension-polymerized under the same conditions as in Example 1 with a particle size range of 60 mesh passes and 170 mesh passes through a JIS standard sieve was high-frequency bonded using the same adherend material as in Example 1. Table 3 shows the results of the test and dielectric loss.

[Table] Comparative example 2 Vinylidene chloride 60 mol%, vinyl chloride 40 mol%
The vinylidene chloride copolymer is an amorphous vinylidene chloride copolymer that shows no crystal melting point or heat of fusion when measured by DSC. Table 4 shows the results of high-frequency bonding using a spherical high-frequency adhesive with a JIS standard sieve pass of 60 mesh and 170 mesh using the same material to be bonded as in Example 1, and the results of dielectric loss.

[Table] Comparative Example 3 Vinylidene fluoride 75 obtained by suspension polymerization
Melting point 85 with a composition of mol%, tetrachloroethylene 10 mol%, hexafluoropropylene 15 mol%
Using a terpolymer of
We tried high-frequency bonding. After applying pressure and high frequency,
It peeled off easily by hand, making it impossible to measure the adhesive strength. The industrial advantages of the present invention are summarized above. It is a dry powder high-frequency adhesive that easily wets metal, glass, wood, fibrous materials, etc. and has practical adhesive strength. Easy to store and handle. After coating and impregnating, excess powder can be recycled and used without loss. The bonding process is easy to automate and inline. High-frequency adhesive strength can be controlled by applying high-frequency voltage, applying temperature, and applying pressure.

Claims (1)

[Claims] 1. Vinylidene chloride component (A) of 64 mol% or more and 93 mol% or less and 7 mol% or more and 36 mol% of one or more monomers copolymerizable with component (A). 0 mol% selected from the following monomers (B) and functional monomers copolymerizable with component (A) and/or component (B)
The above is a crystalline vinylidene chloride copolymer consisting of 10 mol% or less of the monomer component (C), the copolymer has a non-functional group at the end, and has a particle size of 1μ or more and 500μ.
Below is a spherical shaped powdered high frequency adhesive. 2. The high-frequency adhesive according to claim 1, wherein component (B) comprises a monomer unit selected from α-monosubstituted unsaturated ethylenically monomers and unsaturated carboxylic acid ester monomers. 3 (C) component is unsaturated carboxylic acid, dicarboxylic acid,
Claims 1 or 2 comprising one or more monomer units selected from α-alkyl substituted carboxylic acids, acid amides thereof, hydroxyalkyl esters, and glycidyl (alkyl) esters. High frequency adhesive. 4 Claims 1 to 4, in which the copolymer is melted or softened and/or crosslinked by high frequency dielectric
The high-frequency adhesive according to any one of Item 3. 5. The high-frequency adhesive according to any one of claims 1 to 4, wherein the copolymer has a dielectric loss of 0.02 or more. 6. The high-frequency adhesive according to any one of claims 1 to 5, wherein the copolymer has a total wetting property value of 1.0 or more and 200 or less.