JPS6253911B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a surface heating element, and particularly to a manufacturing method suitable for attaching a carpet base to a thermally conductive metal foil whose surface is treated with a resin, such as aluminum foil, which is laminated on a heating conductor such as an electric carpet. Conventionally, in the production of electric carpets, solvent-based adhesives have generally been used to attach carpet fabric, which is fiber cloth, to thermally conductive metal foil.
There are problems with safety and health, environmental protection, and the bonding process, so it is desirable to use a solvent-free adhesive. In other words, in order to perform bonding work quickly, solvent-based adhesives with excellent initial adhesion strength are recommended, but the use of solvents poses safety and hygiene issues, especially the risk of fire, and organic solvent discharge equipment is required in terms of equipment. , solvent drying equipment, and in the case of spray application, additional equipment such as scattering prevention equipment is required. Furthermore, when attaching a carpet to a heat conductive metal foil, since solvent-based adhesives have excellent initial tackiness, it is difficult to correct misalignment after lamination, resulting in poor yields, and it cannot be said to be a practical method. Therefore, in order to solve the problems of solvent-based adhesives,
The use of hot melt adhesives and water-based adhesives is being considered. However, when hot-melt adhesives are used, if the adhesive strength at high temperatures and heat-resistant adhesive durability required for surface heating elements are increased, the initial adhesive strength, which is a characteristic of hot-melt adhesives, can be satisfied. , the pot life (tatsu clean range) from application to lamination is short, and
The adhesive layer after solidification has poor flexibility, which impairs the drape properties of the resulting carpet, and is also inconvenient for folding and packaging. On the other hand, when using a hot-melt type adhesive similar to an adhesive type, the adhesive strength when heated when used on a carpet is poor, and it is difficult to say that it is suitable for manufacturing a physical top heating element. In addition, when using a water-based adhesive, there are no difficulties in correcting the position during bonding, but the initial adhesive strength is slow to develop, and productivity can be improved even if heat drying equipment is installed before and after applying the adhesive and bonding. There are drawbacks that prevent it from being a fundamental countermeasure. In view of the special circumstances in the production of such surface heating elements, the present inventors have conducted intensive research and have developed a two-component urethane adhesive that uses a water-soluble urethane prepolymer as its main ingredient and a curing agent that has water as its main ingredient. The present inventors have discovered that the various difficulties described above can be overcome when used in the manufacture of surface heating elements, leading to the completion of the present invention. In other words, although urethane adhesives generally have the disadvantage of gas foaming due to moisture, they are highly flexible, heat resistant, and can be easily made solvent-free, so they have recently been widely used in various applications, but polyols, Two-component curing types that use amines etc. as curing agents have problems with mixing the two components, curing speed, toxicity, etc.
On the other hand, one-component adhesives that use moisture in the air or moisture contained in the adherend have problems with curing speed, temperature and humidity dependence, foaming properties, storage stability, etc. It cannot be said that these agents are sufficient to be used for the purposes of the present invention in place of agents. However, the present inventors investigated the curing mechanism of water-soluble urethane prepolymers, which had not been developed for adhesive applications, using curing agents mainly composed of water. Not only does the agent dissolve and diffuse into the urethane prepolymer very quickly, resulting in rapid curing with significant foaming, but especially when used to bond porous fabrics such as carpet, the gas generated can The foam layer that remains permeates through the fabric and hardens to fill the gaps in the woven fabric, exhibiting a good anchoring effect, and the adhesive layer becoming a slight foam, which improves the adhesion and drapability of the carpet. It was found that no damage was caused. In addition, by using water as the main component of the curing agent, it can be applied in an extremely simple manner, and the application timing, application process, etc. can be easily selected, and there are no problems in terms of safety, hygiene, or environmental conservation. , it is easy to select a non-toxic curing accelerator for this curing system, and it has excellent coating workability on large adherends, and it is also easy to use, as it does not require two-component mixing or special equipment for coating. It has also been found that it is also excellent. Therefore, the present inventors focused on the above-mentioned adhesive properties of such a water-soluble urethane prepolymer and a curing agent mainly composed of water, and applied it to the bonding process between a thermally conductive metal foil whose surface has been treated with a resin and a fibrous surface material. As a result, they discovered that while providing initial adhesion comparable to solvent-based and hot-melt adhesives, they do not impair drapability, which is essential for product quality, and also provide excellent advantages in application work, and have developed the present invention. It has come to completion. That is, in the present invention, when manufacturing a surface heating element by laminating a heat conductive metal foil whose surface is treated with a resin on the heat conductive wire and then laminating a fibrous surface material on the heat conductive metal foil, the heat conductive metal foil or At least one of the fibrous surface materials is coated or sprayed separately using a curing agent containing a water-soluble urethane prepolymer as the main ingredient and water as the main ingredient, or
Alternatively, after spraying at the same time so that they are mixed in space, the heat conductive metal foil and the fibrous surface material are overlapped,
An object of the present invention is to provide a surface heating element that is bonded by pressing. Hereinafter, the present invention will be explained based on specific steps in manufacturing a surface heating element. In the present invention, the thermally conductive metal foil with a resin-treated surface to be laminated on the heat-generating conductor is generally an aluminum foil having a predetermined size and a thickness of several tens of microns, with a thin plastic sheet laminated on the surface layer. When laminating a brushed carpet fabric as a fibrous surface layer material to the aluminum foil, a low viscosity base material mainly composed of a solvent-free water-soluble urethane prepolymer is usually coated on the aluminum foil using a roll coater, a flow coater, or a perforated coating. Apply with a roller or spray uniformly over the entire surface or in the form of beads, dots, etc. Next, water containing a small amount of a curing accelerator is used as a curing agent, and a required amount of water containing a small amount of a curing accelerator is applied to the active NCO group contained in the main coating agent, for example, by spraying. Immediately, the compatible water and the base agent begin to react, foaming and expanding, and becoming cloudy. Therefore, within several tens of seconds, before a hardened skin layer has formed, the carpets are placed on top of each other, and immediately
When pressed with a roller or press at a rate of about ² g/cm, practical adhesive strength is reached within a few minutes at room temperature. When the curing agent is used in large excess relative to the water-soluble urethane prepolymer, the remaining moisture is removed at room temperature or by forced drying, and the product is moved to the next step such as packaging. Good adhesive strength can also be obtained by spraying water on the packing surface (adhesive surface) of the carpet in advance and then overlapping the aluminum foil coated with the main agent. The most preferred method is to spray the base agent and the curing agent simultaneously using a double-headed gun, and a commercially available double-headed gun can be used.
In this case, airless spraying is preferred to avoid overspray. When the base ingredient has a high viscosity, it is preferable to hot spray it. This double-head gun spraying method has the advantage that mixing and compatibility with water is improved, the working speed can be further increased, and at the same time, the amount of water used is small, and there is almost no need for subsequent drying. The base agent and/or curing agent may be applied to any surface, but it is preferable to apply both to aluminum foil because a small amount of application is required. It is also advantageous because the reaction rate is fast and heating is not particularly necessary. The urethane prepolymer used in the present invention is produced by reacting a specific polyalkylene ether polyol with an excess of polyisocyanate, and the molar ratio of ethylene oxide in the polyalkylene ether polyol is preferably 30 to 90%. Such polyalkylene ether polyols typically include
It is produced by adding ethylene oxide to a compound containing two or more hydroxyl groups in a molar ratio of 30 to 90%. For example, compounds containing two or more active hydrogens include ethylene glycol,
diethylene glycol, propylene glycol,
Manufactured by adding or co-adding ethylene oxide or other alkylene oxides such as propylene oxide, butylene oxide, etc. using dipropylene glycol, glycerin, trimethylolpropane, pentaerythtol, sorbitol, sucrose, etc. using a known method. be done. Considering hydrophilicity and workability, the molecular weight of polyalkylene ether polyol is 1,000 to 20,000, especially 1,000 to 20,000.
A range of 5000 is preferred, and among polyalkylene ether polyols, polyalkylene ether diols are preferred. As the polyisocyanate, those used in the production of ordinary urethane prepolymers can be used, such as toluene diisocyanate and diphenylmethane-4,
Purified products and crude products of 4′-diisocyanate are used. In particular, diphenylmethane-4,4'-diisocyanate is suitable from the viewpoint of physical properties such as odor, workability, curability, adhesiveness, and toxicity, and cost. The ratio of polyalkylene ether polyol to polyisocyanate is NCO/OH=
It may be determined depending on the range of 3.0 to 6.0 equivalents, and the urethane prepolymer obtained preferably has 4 to 13% of residual active isocyanate groups and a viscosity of 3,000 to 10,000 cps in terms of reactivity, workability, performance, etc. Of course, such urethane prepolymers contain fillers,
Anti-aging agents, color pigments, reaction catalysts, adhesion agents,
A solvent and a plasticizer may be added as necessary. The curing agent mainly composed of water used in the present invention is mainly composed of water having an active hydroxyl group that reacts with the active isocyanate group of the urethane prepolymer.
It is preferable to add various reaction catalysts to form an aqueous solution that can be sprayed. This catalyst includes organic amines such as triethylenediamine, triethylamine, dimethylethanolamine, tetramethylpropylenediamine, and tetramethylenetriamine, as well as inorganic basic compounds such as boric acid and sodium hydroxide, urea, thiourea, amino acid salts, and basic Many things such as amino acids can be used, but from the viewpoint of toxicity, odor, water solubility, economic efficiency, etc., inorganic basic compounds, urea, thiourea, amino acid salts, and mixtures of two or more of basic amino acids are particularly recommended. It is preferable to use Adhesion promoters, dyes and pigments, fillers, surfactants, etc. may be added to the curing agent as necessary. In particular, by adding a surfactant, the compatibility with the urethane prepolymer is improved, and by adding dyes and pigments, it is possible to check the mixing of the sprayed surface, the amount of coating, etc. Furthermore, by adding a filler, it is possible to prevent penetration into porous materials and reduce costs. As detailed above, according to the present invention, there is little environmental pollution in the work line, safety and hygiene are achieved through solvent removal, initial adhesion comparable to hot melt adhesives, ultra-fast adhesives without the need for heating, etc. Various unprecedented advantages such as hardenability, productivity, and energy saving can be obtained. In addition, compared to conventional adhesives, such two-component adhesives allow a wide range of selection in the mixing ratio and degree of mixing of the base agent and hardening agent, and even if a large excess of hardening agent is used, the remaining water only evaporates. for,
The usage is quite simple, which makes management easier. In terms of physical properties, we manufacture surface heating elements with flexibility comparable to rubber-based solvent-based adhesives, excellent adhesion by penetrating porous surfaces, intertwining, and anchoring effects, and excellent handling, texture, and durability. can do. Hereinafter, the present invention will be explained in more detail based on specific examples. Production Example 1 (Production of urethane prepolymer) Diphenylmethane-4,4 to 200 parts by weight of polyalkylene ether diol with an average molecular weight of 3000 (trade name Adeka Polyether PR3007, manufactured by Asahi Denka Co., Ltd., ethylene oxide 70% molar ratio) ′-Add 100 parts by weight of diisocyanate (NCO/OH ratio = 6.0) to a stirrable container with a heating jacket,
The mixture was mixed and reacted at an elevated temperature of 80° C. for 3 hours to obtain a water-soluble urethane prepolymer having a residual active isocyanate group of 9.33% and a viscosity of 6000 cps. Production Examples 2 to 7 (Production of urethane prepolymers) Polyalkylene ether polyols shown in Table 1 below were prepared in the same manner as in Production Example 1 using diisocyanates shown in Table 1 below, with water-soluble properties shown in Table 1 below. Obtain a urethane prepolymer.

[Table] Production Examples 8 to 13 (Curing agent containing water as a main component) The components shown in Table 2 below are dissolved in water at a predetermined ratio to obtain a curing agent used as a reaction catalyst for urethane prepolymer.

【table】

[Table] Example 1 (Manufacture of electric carpet) An aluminum film whose surface was treated with a resin as a conductive metal foil was laminated on the surface of the cushioned lower layer of the felt in which the heat-generating conductor was embedded, and the surface of the aluminum film was coated with the same material as in Production Example 1. The prepared water-soluble urethane polymer was applied at a rate of 75 g/m ² , and then the water-based curing agent prepared in Production Example 9 was applied onto the coated surface at a rate of 35 g/m ² using an airless sprayer. Immediately, the raised carpet surface layer material was layered on top of the other, and the material was lightly pressed with a roller to adhere. As a result of measuring the peel adhesion strength using the usual method while curing at room temperature, it was 0.5 Kg/in after 1 minute and 1.0 Kg/in or more after 2 minutes, making it a practical adhesive that can be packed and shipped after 10 minutes. It was getting stronger. It was sufficiently cured in about 1 minute in a heated atmosphere of 80°C, and the same practical adhesive strength as above was obtained. Example 2 In Example 1, a water-soluble urethane prepolymer and a curing agent mainly composed of water were simultaneously sprayed using an airless double-headed gun, mixed in the air, applied onto an aluminum film, and immediately covered with a raised carpet. An electric carpet is manufactured in the same manner as in Example 1, except that the parts are combined and bonded by pressing lightly with a press. The peel adhesion strength was measured in a conventional manner while being cured at room temperature, and after 1 minute it was 1.3 kg/in, and after 5 minutes it had reached a practical adhesive strength that could be packed and shipped. Adhesion strength is 1.0 in 30 seconds in a heated atmosphere of 80℃
Kg/in or more, and it was observed that practical adhesive strength was obtained. Examples 3 to 14 Electric carpets were manufactured in the same manner as in Example 1, except that the combinations of urethane prepolymer and water-based curing agent were as shown in Table 3 below. Table 4 also lists evaluations of 1) application workability, 2) solubility in water, 3) curing speed, 4) adhesive strength development, and 5 adhesive strength necessary for carrying out the method of the present invention. Note that: 1. Application workability is determined by whether the urethane prepolymer can be applied with a roll coater or sprayed. Generally, if the viscosity of the urethane prepolymer exceeds 10,000 ops, it is difficult to apply with a roller coater or spray. 2 Solubility in water is evaluated by placing urethane prepolymer and curing agent in a 2:1 ratio in a beaker and stirring. ○ indicates complete dispersion within 10 seconds, △ indicates dispersion within 10 to 30 seconds, and × indicates no dispersion even after 30 or more stirrings. 3. The curing speed is evaluated by taking the urethane prepolymer and curing agent at a ratio of 2:1 in a beaker, stirring for 10 seconds, and then measuring the time required for curing until there is no finger tack. ◎ indicates within 1 minute, ◯ indicates 1 to 2 minutes, △ indicates 2 to 3 minutes, and × indicates 3 minutes or more. 4. Adhesive strength development was determined by applying a predetermined amount of polyurethane prepolymer onto an aluminum film whose surface had been treated with resin, then applying a hardening agent, immediately overlaying the raised carpet, pressing lightly, and placing it in an atmosphere of 25℃ x 65% RH. The evaluation is based on the time it takes for an adhesive force of 1 kg/in or more to develop. Adhesion strength was measured by performing a 180 degree peel test using a push-pull gauge. 5 Adhesive strength is evaluated by the adhesive strength after 10 minutes of bonding under the same conditions in the test in 4 above. Practical adhesive strength should be 1Kg/in or more, so 〇 is 1
Kg/in or more, × indicates less than 1 Kg/in.

[Table] As is clear from the above results, the polyurethane prepolymer used in the method of the present invention not only has good application workability, but also has good solubility in water, so it has an excellent curing speed, and 1Kg/ Peel adhesion strength of in or higher is developed within 3 minutes in an atmosphere of 25°C x 65% RH, and practical adhesive strength is developed within 1 minute in a heated atmosphere of 80°C. The final adhesive strength is also sufficient.

Claims (1)

[Scope of Claims] 1. In manufacturing a surface heating element by laminating a heat conductive metal foil whose surface is treated with resin on a heat conductive wire and then laminating a fibrous surface material on the heat conductive metal foil, the heat conduction Apply or spray them separately, or mix them in space, on at least one of the metal foil or the fibrous surface material, using a water-soluble urethane prepolymer as the main ingredient and a curing agent containing water as the main ingredient. A method for producing a surface heating element, which is characterized in that the heat conductive metal foil and the fibrous surface layer material are overlapped and bonded by pressing after spraying at the same time so as to cause the heat conduction to occur. 2. The production method according to item 1, wherein the water-soluble urethane prepolymer is a reaction product of a polyalkylene ether polyol containing ethylene oxide and an excess polyisocyanate. 3 The curing agent whose main component is water is obtained by mixing water with one or more reaction catalysts selected from organic amines, inorganic basic compounds, urea, thiourea, amino acid salts, or basic amino acids. 2. The manufacturing method according to item 1, which uses a curing agent.