JP4544853B2 - Method for producing flame retardant sealing material - Google Patents

Description

The present invention relates to a method for producing a flame-retardant sealing material . More specifically, the present invention has both excellent sealing properties and flame retardancy, and is used in a severe environment such as a high-temperature atmosphere or a highly exothermic electron. The present invention relates to a method for producing a flame-retardant sealing material that can be suitably used for equipment, precision equipment, and the like.

  A display unit such as a liquid crystal display, a microphone unit, and other input / output units such as a speaker unit are provided in an electric device such as a mobile phone, a television, and other computer displays. Such an input / output unit is provided in a portion where the electrical equipment casing is open to the outside. For example, in the case of liquid crystal, a small gap between the opening and the liquid crystal causes intrusion of dust and liquid crystal display. A sealing material for preventing light leakage of the backlight used and rattling of the casing is disposed between the periphery of the liquid crystal and the casing. And in recent years, due to the demand for higher functionality and weight reduction of mobile phones and the like, such sealing materials are also required to be small and thin, and as a material constituting such sealing materials, A low-hardness polyurethane foam having an excellent flexibility to play a role as a sealing material even if it is thin is suitable. Furthermore, polyurethane foams can be suitably used for sealing materials installed in electrical equipment casings because of less material settling and gas generation (migration).

  However, while the sealing material made of polyurethane foam has good properties as a sealing material, it is an organic material, has a high specific surface area, and further has a thin sheet shape. There is a problem with flame retardancy when it is assembled in an electric / electronic device casing that may become high temperature due to heat generation. On the other hand, generally, (1) halogenated flame retardants such as organic bromine compounds and organic chlorine compounds, (2) organic phosphorus compounds, (3) antimony trioxide or (4) metals A method of making flame retardant by using one or more flame retardants such as hydroxides in combination has been widely adopted.

However, when the substances (1) to (4) are used, the following problems are pointed out. That is,
(1) Halogen compounds are not suitable for use as flame retardants because they generate halides with a large environmental load upon combustion.
(2) When an organophosphorus compound is used as a flame retardant, it is difficult to ensure sufficient safety because it is highly toxic to the human body, and problems such as strength deterioration and migration of the resulting polyurethane foam, polyurethane There may be a case where an adverse effect such as reaction inhibition at the time of foam formation is given.
(3) Antimony trioxide is not suitable for use because both the environmental impact of (1) and the harmfulness of (2) have been confirmed.
(4) When a metal hydroxide such as aluminum hydroxide or magnesium hydroxide is used as a flame retardant, there are almost no environmental and human problems mentioned above, and a safe sealing material can be produced. On the other hand, in order to achieve the flame retardancy prescribed in, for example, UL94 (a weak electric-related packing material / soundproof material), it is necessary to mix a large amount of metal hydroxide in the raw material of the polyurethane foam. In this case, physical properties that are useful as a sealing material such as low hardness, which is inherently exhibited by the polyurethane foam, are impaired. In addition, the flame retardance prescribed | regulated to UL94 is evaluated by the combustion distance, time, etc. of the test piece (mounted on the metal net 42) with respect to the direct fire of the Bunsen or the chillyl burner 44 implemented by the experimental apparatus 40 as shown in FIG. In the case of the HBF standard, either (1) the burning speed between 100 mm does not exceed 40 mm / min, or (2) the flame or glow disappears before reaching the 125 mm mark, has been achieved. Evaluation is carried out depending on whether or not.

In order to overcome the above-mentioned problems and achieve the intended purpose, a method for producing a flame-retardant sealing material according to the present invention includes :
Against Po polyol 100 parts by weight, only the metal hydroxide obtained by setting the average particle size in the range of 10~100μm as a solid component with mixing in the range of 25 to 50 parts by weight, a material capable of reacting with an isocyanate Diluted in advance with a polyol as a solvent, mixed a liquid mixture in which the auxiliary material and metal catalyst were set so that the content of the foam stabilizer is in the range of 30 to 70% by weight, isocyanate, and foaming gas To obtain a foam material by mechanical flossing,
The foam raw material is supplied onto a base film fed from a supply roll,
The foam raw material supplied on the base film is adjusted by the product thickness control means so that the thickness of the elastic sheet obtained is in the range of 0.3 to 3.0 mm,
By reacting and curing the foam raw material, an elastic sheet is formed on the base film,
The product recovery roll winds and collects the elastic sheet together with the base film,
By setting the thickness of the elastic sheet in a range of 0.3 to 3.0 mm and setting the density of the elastic sheet in a range of 240 to 500 kg / m ³ , a 25% compression load (25% CLD) is set. The flame retardant seal in which the flame retardancy specified in UL94 achieves the HBF standard by setting the content of the substance that can be dissolved in acetone in the elastic sheet to 5.0 wt% or less. It is characterized by obtaining materials.

As described above, a metal hydroxide having an average particle size set in a range of 10 to 100 μm is mixed in a range of 25 to 50 parts by weight with respect to 100 parts by weight of a polyol, and a substance capable of reacting with an isocyanate. Diluting a certain polyol in advance as a solvent, mixing a mixture of secondary materials and metal catalyst set so that the content of the foam stabilizer is in the range of 30 to 70% by weight, mixing isocyanate and foaming gas According to the flame-retardant sealing material comprising an elastic sheet obtained by the mechanical floss method, the elastic sheet has a thickness of 0.3 to 3.0 mm and a density of the elastic sheet of 240 to 500 kg / by setting the range of m ^3, 25% compressive load of (25% CLD) not more than 0.03 MPa, the content of a substance capable of dissolving in acetone in the elastic sheet, 5.0 By the following amount%, flame retardancy as specified in UL94 can achieve a HBF standards. That is, according to the flame-retardant sealing material obtained by the production method according to the present invention , the flame retardancy that achieves the HBF standard defined in UL94 and the sealing property that the 25% compression load is 0.03 MPa or less. Can have both. Moreover, according to the manufacturing method of a flame-retardant sealing material, since a flame-retardant sealing material can be continuously manufactured as a long thing, the manufacturing cost can be reduced significantly.

  Next, the flame-retardant sealing material according to the present invention will be described below with reference to the accompanying drawings by way of preferred examples. The inventor of the present application uses a polyurethane foam having a very low content of unreacted monomers and low-molecular oligomers, etc., which volatilizes by heating to become a combustible gas component and inhibits flame retardancy, and is also highly volatile low The sealing material manufactured by adopting a mechanical floss method that can avoid the use of amine catalyst, which is a molecular substance, and suppressing volatilization related to foam stabilizers essential for foam production is the amount of metal hydroxide mixed It has been found that sufficient flame retardancy and sealing performance can be achieved while reducing the above.

  In the present invention, the flame retardancy and sealability, which are characteristic physical properties of the flame retardant sealing material, are HBF standard (described above [0004]) and 25% compression load (hereinafter referred to as 25% CLD) defined in UL94, respectively. )). The flame retardancy is evaluated by whether or not the HBF standard is achieved, and the sealability is evaluated by whether or not 25% CLD indicating flexibility is 0.03 MPa or less.

  As shown in FIG. 1, the flame-retardant sealing material 10 includes a foamed elastic sheet 12 that achieves required physical properties such as cushioning properties, sealing properties, flexibility, and shape followability, and one surface of the elastic sheet 12. It is basically composed of a base film 14 that is laminated and improves the structural strength of the flame-retardant sealing material 10. The elastic sheet 12 is made of a known mechanical floss method, specifically, polyols and isocyanates as main raw materials, auxiliary raw materials such as a metal stabilizer 16 as a foam stabilizer and a flame retardant, and a foaming gas. Is made into a foam raw material M, and the raw material M is manufactured by molding into a sheet shape. That is, the metal hydroxide 16 is uniformly dispersed in the elastic sheet 12 (see FIG. 1). The contents of the mechanical floss method and the raw materials are described in detail in, for example, Japanese Patent Publication No. 53-8735.

Each physical property value required for the elastic sheet 12 thus obtained is employed as an index of flexibility related to sealing properties. (1) 25% CLD is 0.03 MPa or less, and both sealing properties and flame retardancy (2) Density, which is a related index, is 240 to 500 kg / m ³ , and (3) thickness is 0.3 to 3.0 mm. Here, (1) If the 25% CLD exceeds 0.03 MPa, the flexibility is inferior and sufficient sealing performance is not exhibited. Further, (2) if the density is less than 240 kg / m ³ , the elastic sheet 12 is in a so-called sparse state, so that the contact area with the air becomes large, and the flame retardance cannot achieve the HBF standard, while 500 kg If it exceeds / m ³ , the 25% CLD also increases and the sealing performance deteriorates. (3) If the thickness is less than 0.3 mm, it becomes difficult to exhibit sufficient sealing properties, and the ignitability against direct fire is increased, and the HBF standard defined in UL94 cannot be achieved. . On the other hand, when it exceeds 3.0 mm, it is too thick, and it becomes impossible to incorporate it into a product with limited installation space such as a mobile phone.

  The flame retardancy that achieves the HBF standard defined in (4) UL94 of the flame retardant sealing material 10 is mixed with a predetermined amount of a metal hydroxide 16 that is a flame retardant, and foam control. This is achieved by using a substance capable of reacting with isocyanate such as polyol as a solvent for diluting the agent. As described above, the main raw materials used for producing the elastic sheet 12 are the same polyols and isocyanates as those of ordinary polyurethane foams. If necessary, foaming agents, foam stabilizers, cross-linking agents, plastics are used. The required amounts of various auxiliary materials such as agents and / or catalysts are added. Here, the polyol and isocyanate are set to about 20 to 45% by weight and 25 to 35% by weight, respectively, the foam stabilizer as the auxiliary material is 2 to 3% by weight, the crosslinking agent is 8 to 15% by weight, the catalyst is It is set to about 3 to 5% by weight. In addition, about 50-200 volume% is suitable for the mixing ratio of gas for foaming, such as an inert gas used for a mechanical froth method, with respect to the total volume 100 of each raw material.

  As the metal hydroxide 16, a substance such as known aluminum hydroxide or magnesium hydroxide, which generates water by dissociation of a hydroxyl group (—OH) in the structure when heated, is used. The mixing amount is set to 25 to 50 parts by weight, preferably 30 to 35 parts by weight with respect to 100 parts by weight of the polyol which is the main raw material. If this amount is less than 25 parts by weight, the desired flame retardancy will not be achieved, while if it exceeds 50 parts by weight, it will become hard or brittle, resulting in problems with sealing properties. Moreover, about the metal hydroxide 16, the average particle diameter is set to the range of 10-100 micrometers, Preferably it is 20-60 micrometers. When this value is less than 10 μm, the viscosity of the foam raw material M is increased, or the water content in the foam raw material M is increased to cause a foaming reaction due to the reaction between water and isocyanate. Production of a suitable elastic sheet 12 becomes difficult. On the other hand, if it exceeds 100 μm, it becomes easy to settle when mixed with the foam raw material M, so that it becomes difficult to disperse suitably. Will be inhibited.

  As the foam stabilizer, which is one of the auxiliary materials, known ones such as typical silicone substances are used. The use of this foam stabilizer is indispensable for the production of polyurethane foams by the mechanical floss method, but it is one of the flammable substances due to its low molecular weight, so it becomes an element that hinders the achievement of flame retardancy. ing. In addition, foam stabilizers such as silicone substances are used because they have a very high viscosity when used as they are, and as dilution solvents, for example, isocyanates such as polyols, which are raw materials for polyurethane foams, are used. It is preferred to use a substance that can react with.

  In this case, the foam stabilizer dispersed in the solvent for dilution is in a state in which the polyol as a dilution medium is incorporated into the polyurethane molecule formed by reacting with the isocyanate as the main raw material of the elastic sheet 12. Volatilization, which is an impediment to flame retardancy, is prevented. Moreover, the usage-amount of the solvent for dilution of a foam stabilizer is set so that the content rate of a foam stabilizer may become the range of 30 to 70 weight%. If this value is less than 30% by weight, the role as a foam stabilizer is poor. On the other hand, if it exceeds 70% by weight, the viscosity at the time of using the foam stabilizer becomes high and suitable production cannot be performed.

  Moreover, generally as a solvent which dilutes foam stabilizers, such as a silicone type substance, the low boiling point substance which is a liquid with a low viscosity at normal temperature, such as alkylbenzenes, is used suitably. However, such materials easily volatilize and impair flame retardancy. Furthermore, with regard to substances that volatilize at low temperatures that impair flame retardancy, not only the solvent for dilution, but also a wide variety of substances such as monomers and antioxidants used in the synthesis of the main raw material polyol. Is true. Therefore, the content of a substance that can be dissolved in acetone (hereinafter referred to as acetone-dissolved substance) in the elastic sheet 12 is defined as a condition for the flame retardancy specified in UL94 to achieve the HBF standard. In the present invention, the content of the acetone-dissolved substance is 5.0% by weight or less. When this value exceeds 5.0% by weight, the HBF standard is achieved in the flame retardancy specified in UL94 even when the amount of the metal hydroxide 16 and the condition for the foam stabilizer are satisfied. It has been confirmed not to. The content of the substance that can be dissolved in acetone is measured by, for example, the acetone extraction rate from the elastic sheet 12, and an example of an actual measurement method will be described in an experimental example described later ([0023]). In addition, when low boiling point substances such as alkylbenzenes are used as a solvent for diluting the foam stabilizer, these are present in a free form outside the polyurethane structure in the elastic sheet 12, and so-called migration becomes obvious. There is also a problem to do. Therefore, the use of a substance capable of reacting with an isocyanate such as polyols as a solvent for dilution can also be expected to have the effect of greatly suppressing the above-described migration.

  As described above, the base film 14 is a member that is integrally laminated with the elastic sheet 12 in order to improve the structural strength of the flame retardant sealing material 10 and improve the handling properties of the product. . The base film 14 also serves as a transfer medium for the foam material M in the manufacturing apparatus 30 as described in the manufacturing method described later ([0017]). Therefore, the base film 14 has physical strength capable of resisting the tension applied by the roll mechanism 32 and resistance to heat applied in the tunnel heating furnace 38 in order to react and cure the foam raw material M. For example, it is preferable to use various resins such as PET that are excellent in heat shrinkage, and the thickness varies depending on the material, but is set to several tens to 500 μm, preferably about 25 to 125 μm. If it is this thickness, even if laminated | stacked on the elastic sheet 12, it does not have a bad influence on the sealing performance of the flame-retardant sealing material 10. FIG. As will be described later ([0017]), for example, when the flame-retardant sealing material 10 is molded using a mold, the base film 14 is not necessary, and the flame-retardant sealing material 10 as shown in FIG. 2 is obtained. It is done.

(Example of manufacturing method)
Next, an example of a suitable manufacturing apparatus for the flame-retardant sealing material according to the present embodiment and a manufacturing method using the manufacturing apparatus will be described below. As shown in FIG. 3, the production of the flame-retardant sealing material 10 basically comprises a raw material preparation step S1, a raw material supply / forming step S2, a heating step S3 and a final step S4. It is preferably manufactured. The manufacturing apparatus 30 includes a mixing unit 31 for mixing a main raw material, various auxiliary raw materials, a metal hydroxide 16 and a foaming gas to obtain a foam raw material M of a polyurethane foam by a mechanical floss method, and the foam. A roll mechanism 32 composed of a supply roll 32a and a product recovery roll 32b that serves as a transfer medium for the raw material M and is driven by a drive source (not shown) that is configured by a PET film or the like, and on the base film 14 A discharge nozzle 34 for supplying the raw material M, a product thickness control means 36 such as a knife coater which forms the raw material M in a sheet shape downstream thereof, and a tunnel heating furnace 38 provided downstream thereof. Basically composed. Here, the foam raw material M is reacted and cured on a flat surface, but as described in the above-mentioned Japanese Patent Publication No. 53-8735, it is reacted and cured in a required mold or on release paper. May be.

  The roll mechanism 32 is basically a mechanism that supplies the production line while applying tension to the base film 14 and collects the obtained flame-retardant sealing material 10. And the base film 14 is wound around the supply roll 32a, and it sends out under control. The discharge nozzle 34 supplies the foam raw material M under control onto the substrate film 14 to be transferred, and one end is connected to the mixing unit 31. The raw material preparation step S1 performed in the mixing unit 31 prepares and mixes the foam raw material M of the elastic sheet 12 forming the flame-retardant sealing material 10 to be manufactured from a main raw material and various auxiliary raw materials by a conventionally known method. It is a process to do. Moreover, the product thickness control means 36 makes the foam raw material M discharged and supplied onto the base film 14 into a sheet-like material having a predetermined thickness (0.3 to 3.0 mm (see [0010])). is there. And by passing this part, raw material supply and shaping | molding process S2 is completed. The tunnel-type heating furnace 38 is a part that heats the foam raw material M having a predetermined thickness under control to cause the reaction / curing to proceed to form the flame retardant sealing material 10, which is the foam raw material. Heating process S3 is completed because M passes. In the final step S4, which is the final step, a long product of the flame-retardant sealing material 10 manufactured through the respective steps S1 to S3 is obtained, and a predetermined product that is a final product is obtained as necessary. It is punched into the shape of the sealing material, and further final inspection is carried out. Note that the product may be wound and collected by the product collection roll 32b while being subjected to the final inspection, and shipped as it is. In such a manufacturing form, since the flame-retardant sealing material 10 can be continuously manufactured as a long object of, for example, 5 m or more, the manufacturing cost can be greatly reduced.

(Experimental example)
Below, the flame-retardant sealing material which concerns on this invention is manufactured from the foam raw material of the conditions described in the following Table 1 (Examples 1-8) and Table 2 (Comparative Examples 1-8), and the flame retardance is produced. An experimental example in which sealing performance and the like are evaluated is shown.

For 100 parts by weight of polyether polyol (average molecular weight 3000, hydroxyl value 43.0), 0.1 part by weight of metal catalyst (stannas octoate) and 3 parts by weight of foam stabilizer (silicone substance; for dilution) A solvent) and a metal hydroxide 16 set to the required parts by weight (see Tables 1 and 2), and a mixture of nitrogen (foaming gas) at a flow rate of 0.1 NL / min. ) and, set polyisocyanates as isocyanate index is 0.9 to 1.1 (crude MDI, NCO content: 31%) as mixing and shearing to the foam raw material M and a. The foam raw material M is applied to the elastic sheet 12 from the discharge nozzle 34 onto a base film (made of PET) having a required thickness that is continuously supplied from the supply roll 32 a while being tensioned on the roll mechanism 32. Is supplied so that the density at the time of completion becomes the numerical values described in Tables 1 and 2, and the thicknesses described in Tables 1 and 2 are set by the product thickness control means 36. Then, heating is carried out for 1 to 3 minutes under conditions of 150 ° C. to 200 ° C. in a tunnel-type heating furnace, and the reaction and curing of the foam raw material M proceeds to obtain a flame-retardant sealing material made of the elastic sheet 12. The product is collected by the product collection roll 32b.

The used metal hydroxide 16 and foam stabilizer are as follows.
・ Metal hydroxide: Aluminum hydroxide (trade name Heidilite H-21 (average particle size 25 μm); Showa Denko)
・ Foam stabilizer:
(A) Product name L-5617; manufactured by OSI (a material containing polydimethylsiloxane and polyoxyalkylene as a solvent for diluting to 50% by weight).
(B) Trade name L-5614; OSI (substance made of polydimethylsiloxane and polyoxyalkylene with 50% by weight of alkylbenzene as a solvent for dilution.

  And from the flame-retardant sealing materials according to Examples 1 to 8 and Comparative Examples 1 to 8 produced according to the contents of Table 1 and Table 2, the base film is peeled off to obtain flame retardance of required thickness × 150 mm × 50 mm. A test piece of 25% CLD having a required thickness × φ50 mm and a test piece of 1 g of acetone-dissolved substance (acetone extraction rate) were obtained, and 25% CLD (MPa) and acetone-dissolved were obtained. The acetone extraction rate (%) was measured with respect to the content of each of the materials, and the flame retardancy specified in UL94 was evaluated as ◯: Achieving the HBF standard, X: Not achieved. From here, the suitability as a flame-retardant sealing material according to the present invention was evaluated as ◯: conformity, x: unsuitable. In addition, in relation to the acetone extraction rate, whether or not alkylbenzene was contained was also evaluated with and without. Measurement methods and conditions are as follows.

(Measurement method / conditions)
Density: Measured based on JIS K 6401.
・ Flame retardance: Evaluated according to HBF standard defined in UL94.
-Content of acetone-dissolved material (acetone extraction rate): The weight of the test piece is set to A (here 1 g), and this is extracted by heating and refluxing with acetone as a solvent for 3 hours using a Soxhlet extractor. The extract is dried and the weight is calculated as B from the following formula.
: Content of acetone dissolved substance (acetone extraction rate) = B / A (1) × 100 (%)
-Alkylbenzene content: The above-mentioned extract was evaluated by performing spectral analysis using GC-MS (trade name QP-5000; manufactured by Shimadzu Corporation).

(result)
The results are listed in the following tables. From Table 1 and Table 2, it was confirmed that a flame-retardant sealing material having both flame retardancy and sealing performance can be obtained by setting each physical property value and the like within the range set in the present invention.

1 is a schematic perspective view showing a flame-retardant sealing material according to a preferred embodiment of the present invention with a part cut away. It is a schematic perspective view which shows the flame-retardant sealing material which is not provided with a base film. It is process drawing which shows the manufacturing method of the flame-retardant sealing material which concerns on an Example. It is an example of the manufacturing apparatus which manufactures the flame-retardant sealing material which concerns on an Example. It is the schematic perspective view which shows (a) whole, and (b) the enlarged view which shows the test piece vicinity of the experimental apparatus which implements the flame retardance test prescribed | regulated to UL94.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flame-retardant sealing material 12 Elastic sheet 14 Base film 16 Metal hydroxide M Foam raw material

Claims (1)

A polyol which is a substance capable of reacting with isocyanate while mixing only a metal hydroxide having an average particle size of 10 to 100 μm as a solid component in a range of 25 to 50 parts by weight with respect to 100 parts by weight of a polyol. Is diluted in advance as a solvent, and the liquid mixture in which the auxiliary raw material and the metal catalyst are set so that the content of the foam stabilizer is in the range of 30 to 70% by weight, the isocyanate, and the foaming gas are mixed. To obtain a foam material by mechanical flossing,
The foam raw material is supplied onto a base film fed from a supply roll,
The foam raw material supplied on the base film is adjusted by the product thickness control means so that the thickness of the elastic sheet obtained is in the range of 0.3 to 3.0 mm,
By reacting and curing the foam raw material, an elastic sheet is formed on the base film,
The product recovery roll winds and collects the elastic sheet together with the base film,
By setting the thickness of the elastic sheet in a range of 0.3 to 3.0 mm and setting the density of the elastic sheet in a range of 240 to 500 kg / m ³ , a 25% compression load (25% CLD) is set. The flame retardant seal in which the flame retardancy specified in UL94 achieves the HBF standard by setting the content of the substance that can be dissolved in acetone in the elastic sheet to 5.0 wt% or less. A method for producing a flame-retardant sealing material, comprising obtaining a material.

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