JPS6133873B2 - - 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, easily wets metals, glass, wood, fibrous materials, etc., and has practical high-frequency adhesive strength. Conventionally, as high-frequency adhesives, there have been film-like high-frequency adhesives made of soft polyvinyl chloride film or low-melting point polyamide film, and film-like high-frequency adhesives made of polyvinyl chloride latex or polyvinylidene chloride copolymer latex. Ta. Recently, high-frequency adhesives made of polyvinyl chloride powder or low-melting polyamide powder have been developed, but the dielectric loss is too small and the total wetting characteristic value is too small, and the high-frequency adhesive strength is insufficient to withstand practical use. There is no powdered high frequency adhesive. High-frequency adhesives have attracted particular attention in recent years because they have the following three major advantages. Before adhesion, it is easy to store and handle as a film or powder. 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 the miniaturization, precision, and reliability of high frequency generators and their electronic control mechanisms, high frequency bonding machines have become smaller, less expensive, and integrated in-line into various continuous bonding processes. For example, high-frequency bonding machines are extremely effective in the process of continuously manufacturing bonded structures that are produced in small quantities in large quantities at high speeds, or in processes that continuously produce bonded structures in large quantities in small quantities at high speeds. Examples of specific products for which such high-frequency adhesive machines are effective are: Industrial textile materials (sewing tents and seats) Plywood/laminated wood Unit furniture Interior materials (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.
Melting or Softening Must be a crosslinking and hardening material. 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. Examples of materials that generate high-frequency dielectric heat generation include polyvinyl chloride resin, polyvinylidene chloride resin, and polyamide resin; examples of the latter include phenol, urea, resorcinol,
Melamine resins are known. 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 the following four drawbacks. (1) It is a wet type containing a large amount of water or alcohol, making it difficult to handle and store. (2) Water or alcohol must be evaporated, a drying process is required, 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 inherently dry, but
There are the following four difficulties. It is difficult to position the film adhesive and the material to be adhered, and a slight external force can cause the alignment to shift. The film must be cut depending on the size of the material to be adhered, and even if scraps of film occur, they cannot be reused and are lost. The film insertion process is difficult to automate and difficult to incorporate as an in-line system. Nylon film has poor wetting properties, and polyvinyl chloride and polyvinylidene chloride are easily altered in the film formation process, and plasticizers, etc. must be used, which limits the ability to improve wetting with the bonded material and prevents peeling at the adhesive interface. This may occur in some cases. 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. The adhesive is easily integrated into in-line systems. Wetting with the adhered material can be easily controlled. In response to the above requirements, as a result of intensive research, 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, 20 mol% or more, 93
mol% or less of vinylidene chloride component (A), 7 mol% or more of one or more monomers selected from monomers copolymerizable with component (A), and 80 mol% or less of monomer (B), component (A), and/or Alternatively, it is a vinylidene chloride copolymer consisting of a monomer component (C) of 0 mol% or more and 10 mol% or less selected from functional monomers copolymerizable with component (B), and the copolymer ends are functional. A powdered high frequency adhesive of vinylidene chloride copolymer is provided. Specific requirements of the invention and examples thereof will be shown below, but the invention is not limited to the content thereof. The adhesive of the present invention is produced by emulsion polymerization. The emulsion polymerization method using a water-soluble radical initiator has the advantage that sulfuric acid groups, sulfite groups, hydroxyl groups, etc. can be introduced from the terminal ends of the copolymer, and functional groups can be imparted to the terminal ends of the copolymer. In the emulsion polymerization method, for example, acrylic acid,
There is an advantage that functional monomer components such as methacrylic acid, glycidyl methacrylic acid, and 2-hydroxyethyl acrylate can be introduced into the copolymer with good control. If a functional group can be added to the end of the copolymer, the adhesive can improve its wettability to an adherend, increase the adhesive strength at the adhesive interface, and prevent peeling at the adhesive interface. Furthermore, if the functional monomer component can be introduced into the copolymer with good control, the interfacial adhesive force can be increased in the same way as in the above case. When bonding fibers by high frequency, a mixture of a powder with a high molecular weight and a powder with a low molecular weight is also preferred. Particles with a small molecular weight melt or soften and easily penetrate between the fibers, and particles with a large molecular weight contribute to adhesive strength. As a powder manufacturing method using emulsion polymerization method,
For example, emulsion polymerization method in the presence of a conventional radical initiator, chemical salting out method in the presence of a salting out agent, physical salting out method under mechanical shearing force or temperature change, hot air drying method, infrared drying method, It can be manufactured by combining known methods such as microwave drying. For the polymerization, a well-known radical initiator suitable for emulsion polymerization can be employed. As examples, commonly used are sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like. The above radical initiators are also commonly used as Redox radical initiators in combination with water-soluble reducing agents.
Examples of water-soluble reducing agents include mercaptan, sulfite, sodium sulfite, sodium hydrogen sulfite, sodium hydrogen sulfoxylate, and formaldehyde adducts. These initiators are typically used at 0.01% by weight or more and 1.5% by weight or less, preferably 0.05% by weight or more and 0.75% by weight or less, more preferably 0.1% by weight or more and 0.5% by weight or less based on the monomer. used. Polymerization temperature is generally 20℃
to 80°C, preferably 40°C to 70°C. The pH of the aqueous phase in emulsion polymerization ranges from 1 to 6.
The PH, preferably the PH, ranges from 1.5 to 4. Customary emulsifiers are used as emulsifiers. For example, anionic emulsifiers and/or nonionic emulsifiers are used. As examples of the former, potassium dodecyl sulfate, sodium isooctylbenzenesulfonate, sodium lauryl sulfate, diphenyl ether disulfonic acid or its sodium salt are commonly used, and as the latter, nonyl phenyl ether of polyethylene glycol is commonly used. The amount of emulsifier used is usually 0.1% by weight or more and 5% by weight or less for polymerization. As the emulsion polymerization method, conventional batch polymerization method, monomer continuous addition polymerization method, monomer/radical initiator and/or emulsifier continuous addition polymerization method, and seed batch polymerization method can be employed. Calcium chloride, aluminum chloride, aluminum sulfate, etc. are commonly used as chemical salting-out agents. The amount of salting-out agent used is 1% to 10% by weight based on the polymer. 40°C to 80°C is adopted as the salting-out temperature. As a physical salting-out method, a method is commonly used in which the latex is press-fitted into a salting-out tank with a narrow clearance of 1 mm or less, and a stirrer is rotated at a high speed of 1000 rpm or more to mechanically coagulate the latex. The chemically and/or physically salted out wet cake is dried in conventional fluidized drying. As a heat source, hot air, infrared rays, microwaves, etc. can be used. After this, a conventional pulverizer is used to make the particle size uniform, and a sieve can also be used. As the monomer (B) copolymerizable with vinylidene chloride, 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 preferably vinyl chloride, vinyl acetate, methyl acrylate, ethyl acrylate,
Butyl acrylate and acrylonitrile are cheap and good. Vinylidene chloride (A) and/or monomer (B)
The functional monomer (C) copolymerizable with the monomer selected from unsaturated monocarboxylic acids, dicarboxylic acids, α-alkyl unsaturated carboxylic acids, amides of these acids, hydroxyalkyl esters, and glycidyl esters, or mixtures thereof. etc. are used. Preferably, acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, acrylic acid amide, methacrylic acid amide, hydroxyethyl acrylate, and glycidyl methacrylate are used. More preferably, acrylic acid, methacrylic acid, acrylic amide, methacrylic amide, itaconic acid, hydroxyethyl acrylate, and glycidyl methacrylate are easily available industrially. The composition of vinylidene chloride (A) component, (B) component monomer, and functional monomer (C) component is vinylidene chloride 20 mol% or more and 93 mol% or less, (B) component monomer 7 mol% or more and 80 mol%. Below, (C) component monomer 0
It is preferably mol% or more and 10 mol% or less. Preferably, vinylidene chloride is 35 mol% or more and 90 mol% or less, (B) component monomer is 10 mol% or more and 65 mol% or less, and (C) component monomer is 0.05 mol% or more and 8 mol% or less. More preferably, the vinylidene chloride content is 40 mol% or more and 85 mol% or less, the (B) component monomer content is 20 mol% or more and 60 mol% or less, and the (C) component monomer content is 0.5 mol% or more and 5 mol% or less. If the vinylidene chloride content is less than 20 mol%, high-frequency heat generation is so small that the adhesive does not melt or soften sufficiently, making it impossible to obtain practical adhesive strength, which is undesirable. If vinylidene chloride exceeds 93 mol%, high-frequency heat generation will be reduced, the degree of crystallinity of the copolymer will be too high, and the adhesive will not melt or soften sufficiently, 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. For bonding structural materials, e.g. bonding plywood, laminated wood, metal-to-metal or metal-to-other materials, such as plywood, paperboard, hardboard, etc., functional monomer components and/or functional copolymers may be used. It is preferable to have an end. For bonding non-structural materials such as non-woven fabrics and cloth interlining,
The amount of functional monomer may be small. The effect of introducing the functional monomer (improvement of wettability and interfacial adhesion) is exhibited by introducing the functional monomer component in an amount of 0.05 mol % or more. If the functional monomer component exceeds 10 mol %, a water-soluble polymer or a hydrophilic polymer is produced during emulsion polymerization, and when used in an adhesive, water resistance is undesirably lowered. 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 decreases compared to the copolymer without the introduction, which is not preferable. As a method for analyzing component (C), pyrolysis gas chromatography and conductivity measurement are simple and preferable in terms of analytical accuracy. The accuracy of analysis using these methods is up to 1×10 ⁻⁴ mol/g for the copolymer. On the other hand, it is convenient to calculate the number of functional groups at the polymer end of the adhesive obtained by emulsion polymerization method from the average degree of polymerization. It can be calculated with good reproducibility up to 5 x 10 ^-5 mol/g for the copolymer. The particle size range of the powder adhesive is 0.5 μ or more and 1 mm or less for ease of handling. Preferably 10μ or more and 500μ or less, more preferably 100μ or more and 300μ
It is less than μ. When the above particle diameter range is expressed using a JIS standard sieve, it is 16 mesh passes, preferably 32 mesh passes, and more preferably 42 mesh passes and 170 mesh passes. Particles smaller than 0.5μ are difficult to handle as a powder, and tend to cause secondary agglomeration during salting out or drying, making it difficult to handle the powder. Particles larger than 1 mm tend to cause the adhesive to spread unevenly on the adhered material, causing uneven adhesion and making it difficult to collect the powder. Powder adhesives can be applied to the surface of a material to be bonded, piled, baked, or electrostatically attached to fix or adhere to the surface of the material to be bonded, and then stacked or attached to another material to be bonded. Alternatively, a predetermined bonded structure is obtained by applying a high frequency voltage to a portion of the adhesive to melt and/or soften the adhesive, and then cooling the bonded portion. The frequency of high-frequency adhesive machines is only allowed as specified by the Radio Law, but above 10MHz,
100MHz or less is preferable. Below 10MHz, there is a limit to the withstand voltage of the adhesive, and above 100MHz,
High-power vacuum tubes are not manufactured industrially, and local heating of the adhesive occurs, which is undesirable. Currently, frequencies of 13.66, 27.12, and 40.46MHz 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 heat generation to be sufficient to melt and/or soften the adhesive, 27.12MHz, 20
The dielectric loss at °C should be 0.02 or more. Preferably
It is 0.04 or more, more preferably 0.05 or more. If the dielectric loss is less than 0.02, the amount of high-frequency heat generated 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. If wetting is poor, peeling occurs from the interface between the adhesive and the adhered material, and the adhesive strength that can be obtained is only significantly lower than the strength of the adhesive itself. Accurately obtaining interface wetting property values is very difficult. 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 was applied uniformly to an aluminum plate at 150 g/m ² , and the aluminum plate was placed on top of it and bonded for 30 seconds using a 40 MHz, 1 KW (manufactured by Pearl Industries) high frequency adhesive machine. , 2.5cm x 2.5cm as the adhesive surface bonded by high frequency bonding under a pressure of 5Kg/cm ²
The shear adhesion strength of the sample is measured using an Instron tensile tester at a tensile speed of 10 cm/min at 20°C. The adhesive force is RKg/cm ² . Using powdered adhesives made with varying amounts of functional monomer components, aluminum plate samples 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 = △S / △L _S / △R / △L _R △S: Difference in adhesive strength of adhesive containing functional monomer △L _S : Dielectric loss of adhesive containing functional monomer Difference △R: Difference in adhesive strength between adhesives containing no functional monomer △L _R : Difference in dielectric loss between adhesives containing no functional monomer When the total wetting characteristic value is less than 1.0, substantially The effect of the functional monomer component is lost, and interfacial peeling occurs, which is undesirable. Therefore, the total wetting characteristic value defined above must be greater than or equal to 1.0. The larger the total wetting characteristic value, the better.
If the value exceeds 200, it is not practical because the molecular weight and crystallinity must be increased, or the surface of the adhered material must be kept ideally free from contamination. If the practical total wetting characteristic value is less than 1.0, the effect of the functional monomer component is substantially lost, and interfacial peeling occurs, which is undesirable. Although specific examples will be described in detail below, the present invention is not limited only to the examples. Example 1 Vinylidene chloride 60 mol%, vinyl chloride 40 mol%
500 g of the monomer mixture was pressurized into an autoclave containing 500 g of water in which 15 g of sodium lauryl sulfate and 1.5 g of potassium persulfate were dissolved. The autoclave was maintained at 50°C and stirred for 20 hours to allow emulsion polymerization to proceed. The polymerization rate was approximately 98%. Add 10 g of water to this latex, add 50 g of 20% calcium chloride, and raise the temperature to 70°C while stirring.
Stirred for an additional minute to complete salting out. The salted-out material was separated with a cloth and dried in a hot air dryer at 50°C for 2 days. The particle size and dielectric loss of this copolymer, and the results obtained by applying this powder to a paperboard (Jujo Paper Co., Ltd.'s Jupyrite) at 40MHz, 1KW.
15 seconds, 10 seconds using a high-frequency adhesive machine (manufactured by Pearl Industries)
Table 1 shows the adhesive strength when high frequency bonding was performed under Kg/cm ² pressure.

[Table] Example 2 60 mol% vinylidene chloride, 40 mol% vinyl chloride, 0.73 mol% glycidyl methacrylate.
505 g of the monomer mixture was polymerized under the same conditions as in Example 1, salted out, and dried to obtain a copolymerized powder adhesive. The polymerization rate was 99%. The yield of this copolymer was 99.0%. The particle size of this copolymer,
Dielectric loss and total wetting characteristic values are shown in Table 2. Table 2 shows the adhesion strength when this powder was used to bond 3 mm thick aluminum sheets together, 3 mm thick plywood sheets together, and 3 mm thick glass sheets together using high frequency bonding under the same conditions as in Example 1.
Shown below. As is clear from the table, when the total wetting characteristic value is greater than 1.0, the adhesive strength is high.

[Table] Example 3 Vinylidene chloride 89 mol%, methyl acrylate 11
500g monomer mixture of mol% itaconic acid 5g
The mixture was introduced under reduced pressure into the same aqueous phase as in Example 1 in which it was dissolved, and polymerization, salting out, and drying were carried out under the same conditions as in Example 1 to obtain a powder. The polymerization rate was 96%. For comparison, polymerization was carried out under the same conditions as in the example without containing itaconic acid at all.
Salting out and dry powder were also obtained, and the particle size of each
Table 3 shows the dielectric loss and total wetting characteristic values. This powder was applied to No. 5 chemical paper, the same paper was placed on top of it, and high frequency adhesion was attempted under the same conditions as in Example 1. Table 3 shows a comparison of the adhesion strengths.

[Table] Example 4 Out of 505 g of a monomer mixture of 66.3 mol% vinylidene chloride, 31.4 mol% ethyl acrylate, 2.7 mol% methyl acrylate, and 0.9 mol% hydroxyethyl acrylate, 50.5 g was added to the water phase shown below. The seed polymerization was carried out at 50°C for 2 hours under reduced pressure, and the remaining 454.5 g of monomer was added continuously for 12 hours to complete the polymerization at 50°C. The aqueous phase used here was 500 g of water and sodium diphenyl ether disulfonate (Dow Chem.
Dowfox2A1) 0.1% by weight based on the total monomer amount,
Contains sodium persulfate in an amount of 0.12% by weight based on the total amount of monomers. This latex was salted out under the same conditions as in Example 1, dried, and crushed in a crusher.
The powder that passed through the mesh and 200 mesh sieves was collected and used as a powder adhesive. Table 4 shows the dielectric loss and adhesive strength of this powder. For comparison, a monomer mixture without hydroxyethyl acrylate was polymerized under the same conditions as above, salted out, dried, ground, and sieved to obtain a comparative powder adhesive. Table 4 shows the dielectric loss and adhesive strength of this powder. As is clear from Table 4, the powder containing hydroxyethyl acrylate has superior adhesive strength.

[Table] Example 5 Vinylidene chloride 90 mol%, methyl acrylate 10
A monomer containing 5 mol % of acrylic acid was polymerized, salted out, and dried under the same conditions as in Comparative Example 1 to obtain a powder. This powder was baked on a urethane foam under the same conditions as in Example 1, and bonded to a paper board using high frequency. Table 5 shows the adhesive strength and dielectric loss of this powder at this time. For comparison, a monomer mixed with 13 mol% of acrylic acid was emulsion polymerized in the same manner as above, salted out, and the dielectric loss of the dried powder and the adhesive strength measured in the same manner as above are also shown in Table 5. As is clear from the table, when the amount of acrylic acid is too large, the dielectric loss is large, but the adhesion strength is reduced.

[Table] Comparative Example 1 100 g of vinylidene chloride (VDC) 93.5 mol% and vinyl chloride (VC) 6.5 mol% were mixed with water 150 g potassium persulfate.
0.2 g of potassium lauryl sulfate and 3 g of potassium lauryl sulfate, and polymerized at 50° C. for 20 hours. After adding 2 g of water and 10 g of 20% calcium chloride, the mixture was heat-treated at 70° C. for 30 minutes to complete salting out. Drying was carried out at 50°C for 2 days to obtain a powder. The yield was 99%. Another composition is vinylidene chloride 18 mol%, vinyl chloride 82 mol%
100 g was polymerized, salted out, and dried under the same conditions as above to obtain a powder. These powders were applied to a 3 mm thick paper board (manufactured by Nippon Hardboard) and bonded under the high frequency bonding conditions shown in Example 1. Table 6 shows the adhesive strength and dielectric loss of this powder at this time.

[Table] Comparative Example 2 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, high-frequency adhesive in powder form 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 online. High-frequency adhesive strength can be controlled by applying high-frequency voltage, applying temperature, and applying pressure.

Claims (1)

[Scope of Claims] 1. 7 mol% or more and 80% or less of vinylidene chloride component (A) of 20 mol% or more and 93 mol% or less and one or more monomers selected from monomers copolymerizable with component (A). Vinylidene chloride copolymer consisting of monomer (B) and monomer component (C) of 0 mol% or more and 10 mol% or less selected from functional monomers copolymerizable with component (A) and/or component (B). A powdery high-frequency adhesive of a vinylidene chloride copolymer, which is a polymer having a functional group at the end of the copolymer. 2. The powdered high-frequency adhesive according to claim 1, wherein component (B) comprises a monomer unit selected from α-monosubstituted unsaturated ethylenic monomers and unsaturated carboxylic acid ester monomers. 3 (C) component is unsaturated carboxylic acid, dicarboxylic acid,
α-alkyl-substituted unsaturated carboxylic acids, amides of these acids, or hydroxyalkyl esters,
The powdered high-frequency adhesive according to claim 1 or 2, which comprises one or more monomer units selected from glycidyl alkyl esters. 4 The particle size range of the adhesive is 0.5 μ or more, 1 mm
The powdered high-frequency adhesive according to any one of claims 1 to 3, which is the following particles. 5. The powdered high-frequency adhesive according to any one of claims 1 to 6, wherein the adhesive is a copolymer that melts or softens and/or crosslinks upon application of a high-frequency voltage. 6. Any one of claims 1 to 5, wherein the adhesive is a copolymer with a dielectric loss of 0.02 or more.
Powdered high-frequency adhesive described in Section. 7 Claims 1 to 6, wherein the adhesive is a copolymer having a total wetting property value of 1.0 or more and 200 or less.
The powdered high-frequency adhesive according to any one of the above items.