Polyurethane foam, its manufacturing method, and sealing material

Abstract

To provide a polyurethane foam that has no seepage of low-molecular weight siloxane due to a silicone-based foaming agent and has no risk of generation of contact fault of an electronic device due to silicone contamination.MEANS FOR SOLVING THE PROBLEM: A polyurethane foam is formed from a polyurethane foam-forming composition containing a cardanol-based surfactant, in which ethylene oxide or propylene oxide is added to cardanol, as a foam stabilizer. The cardanol-based surfactant is contained in an amount of 1 to 12 pts.mass based on 100 pts.mass of polyol in the polyurethane foam-forming composition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to polyurethane foam, a method for producing the same, and a sealing material. [Background technology]

[0002] Polyurethane foam formed from polyurethane foam-forming compositions is used as a sealant, cushioning material, and the like.

[0003] Some polyurethane foams contain a silicone-based foam stabilizer as a foam stabilizer in the polyurethane foam forming composition (Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-313730 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, polyurethane foam formed from compositions for forming polyurethane foam containing silicone-based foam stabilizers has a problem in that low-molecular-weight siloxanes leach out during use, causing silicone contamination and leading to contact failures in electronic devices. Therefore, it cannot be used in applications related to electronic devices, such as sealing materials for electronic equipment.

[0006] The present invention has been made in view of the above points, and aims to provide polyurethane foam and sealing material that are less likely to cause silicone contamination due to silicone-based foam stabilizers. [Means for solving the problem]

[0007] The first invention is a polyurethane foam formed from a polyurethane foam-forming composition containing a cardanol-based surfactant, which is obtained by adding ethylene oxide or propylene oxide to cardanol, as a foam stabilizer.

[0008] The second invention is characterized in that, in the first invention, the cardanol-based surfactant is contained in 1 to 12 parts by weight per 100 parts by weight of polyol in the polyurethane foam forming composition.

[0009] The third invention is a method for producing polyurethane foam, characterized by mixing a polyurethane foam-forming composition containing a cardanol-based surfactant as a foam stabilizer and allowing it to react and cure.

[0010] The fourth invention is characterized in that, in the third invention, the cardanol-based surfactant is contained in the polyurethane foam-forming composition in an amount of 1 to 12 parts by weight per 100 parts by weight of polyol.

[0011] The fifth invention is a sealing material formed from the polyurethane foam described in the first or second invention. [Effects of the Invention]

[0012] According to the present invention, since the polyurethane foam is formed from a polyurethane foam-forming composition containing a cardanol-based surfactant, which is cardanol to which ethylene oxide or propylene oxide is added, as a foam stabilizer, it is possible to prevent the leakage of low molecular weight siloxanes caused by silicone-based foam stabilizers, and a polyurethane foam and sealing material with a low risk of silicone contamination can be obtained. [Brief explanation of the drawing]

[0013] [Figure 1] The chemical formulas for cardanol and cardanol-based surfactants are shown. [Figure 2] Table 1 shows the formulations and physical properties of the examples and comparative examples. [Figure 3] Table 2 shows the formulations and physical properties of the examples and comparative examples. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below. The polyurethane foam of the present invention is obtained by mixing a polyurethane foam forming composition and allowing it to react and cure. Polyurethane foam can be manufactured using any method, such as mold foaming, slab foaming, or mechanical floss foaming. Molded foaming is a foaming method in which a polyurethane foam forming composition is mixed with a foaming agent, injected into a foam molding mold, reacted to form the inner shape of the mold, and then hardened. Slab foaming is a method in which a polyurethane foam-forming composition is mixed with a foaming agent, continuously discharged onto a conveyor belt, reacted to foam, and then cured. Mechanical floss foaming is a method of foaming and curing a polyurethane foam-forming composition by supplying a raw material, which has been compressed and mixed with a foaming gas as a foaming agent, to an oak mixer or a nozzle with a narrowed tip, and then discharging it from the oak mixer or nozzle to foam, react, and cure. Mechanical floss foaming can be performed using either a continuous molding method, in which the raw material mixed with the foaming agent is continuously discharged onto a release paper, or a mold molding method, in which it is discharged into a mold.

[0015] The polyurethane foam forming composition includes a polyol, a catalyst, a foam stabilizer, a polyisocyanate, and appropriate auxiliary agents. In this invention, the "polyurethane foam forming composition" refers to a composition that does not contain a foaming agent. Polyols are substances that have two or more hydroxyl groups in a single molecule, and polyols for polyurethane foam can be used. Examples include polyether polyols, polyester polyols, polymer polyols, polyether ester polyols, and plant-derived polyols, and one or more of these may be used.

[0016] Examples of the polyether polyol include polyether polyols obtained by adding an alkylene oxide such as ethylene oxide (EO) or propylene oxide (PO) to a polyhydric alcohol such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, or sucrose. The hydroxyl value (OHV) of the polyether polyol is preferably 15 to 2500 mgKOH / g, more preferably 20 to 2000 mgKOH / g, and even more preferably 22 to 1800 mgKOH / g. The functional group number is preferably 2 to 4, and more preferably 2 to 3. The molecular weight is preferably 50 to 8000, more preferably 80 to 6000, and even more preferably 110 to 4000.

[0017] Examples of the polyester polyol include polyester polyols derived from petroleum obtained by polycondensation of an aliphatic carboxylic acid such as malonic acid, succinic acid, or adipic acid or an aromatic carboxylic acid such as phthalic acid with an aliphatic glycol such as ethylene glycol, diethylene glycol, or propylene glycol. The hydroxyl value (OHV) of the polyester polyol is preferably 15 to 1000 mgKOH / g, more preferably 25 to 700 mgKOH / g, and even more preferably 35 to 400 mgKOH / g. The functional group number is preferably 2 to 4, and more preferably 2 to 3. The molecular weight is preferably 200 to 4000, more preferably 300 to 3000, and even more preferably 400 to 2000.

[0018] Examples of polymer polyols include those obtained by graft polymerization of acrylonitrile, styrene, etc., onto polyether polyols or polyester polyols. The hydroxyl value (OHV) of the polymer polyol is preferably 15 to 80 mg KOH / g, more preferably 20 to 70 mg KOH / g, and even more preferably 25 to 60 mg KOH / g. The number of functional groups is preferably 2 to 4, and even more preferably 2 to 3. The molecular weight is preferably 1000 to 6000, more preferably 2000 to 5000, and even more preferably 2500 to 4000. Polymer polyols can improve the strain characteristics of polyurethane foams.

[0019] Examples of polyether ester polyols include those obtained by reacting a polyether polyol with a polybasic acid to produce polyester, or those that have both polyether and polyester segments within a single molecule. Examples of plant-derived polyols include those obtained from castor oil, soybean oil, rapeseed oil, cottonseed oil, and the like.

[0020] As catalysts, amine-based catalysts for polyurethane foam, metal catalysts, etc., may be used alone or in combination. Examples of amine-based catalysts include monoamine compounds, diamine compounds, triamine compounds, polyamine compounds, cyclic amine compounds, alcoholamine compounds, etheramine compounds, etc., and one of these may be used, or two or more may be used in combination. Examples of metal catalysts include organotin compounds, organoiron compounds, organobismuth compounds, organolead compounds, organozinc compounds, etc., and one of these may be used, or two or more may be used. The amount of catalyst is determined as appropriate, but an example is 0.1 to 8 parts by weight per 100 parts by weight of polyol component.

[0021] The foam stabilizer includes a cardanol-based surfactant. Preferably, the foam stabilizer includes a cardanol-based surfactant, and a silicone-based foam stabilizer may be included in a smaller amount than the cardanol-based surfactant. Furthermore, it is even more preferable that the silicone-based foam stabilizer is not included. As shown in Figure 1, cardanol-based surfactants (2) are surfactants obtained by adding ethylene oxide or propylene oxide to cardanol (1). Cardanol is the main component of cashew nut shell liquid and has one phenolic hydroxyl group. The amount of cardanol-based surfactant blended is preferably 0.5 to 12 parts by weight, more preferably 1 to 11 parts by weight, and even more preferably 2 to 10 parts by weight, per 100 parts by weight of polyol. Multiple types of cardanol-based surfactants may be blended.

[0022] Polyisocyanates are those having two or more isocyanate groups in one molecule, and may be aromatic, alicyclic, or aliphatic polyisocyanates. They may also be bifunctional isocyanates having two isocyanate groups in one molecule, or trifunctional or more isocyanates having three or more isocyanate groups in one molecule, and may be used individually or in combination.

[0023] Examples of bifunctional polyisocyanates include 2,4-toluene diisocyanate (TDI), 2,6-toluene diisocyanate (TDI), m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate (MDI), 2,2'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylenediisocyanate, 3, Examples include aromatic compounds such as 3'-dimethoxy-4,4'-biphenylenediisocyanate, alicyclic compounds such as cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and methylcyclohexane diisocyanate, and aliphatic compounds such as butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, and lysine isocyanate.

[0024] An example of a polyisocyanate with two or more functionalities is polymethylene polyphenyl isocyanate (polymeric MDI). Examples of polyisocyanates with three or more functions include 1-methylbenzol-2,4,6-triisocyanate, 1,3,5-trimethylbenzol-2,4,6-triisocyanate, biphenyl-2,4,4'-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, triphenylmethane-4,4',4"-triisocyanate, and the like.

[0025] The isocyanate index is preferably 80 to 130, and more preferably 90 to 120. The isocyanate index is calculated as [(equivalent amount of isocyanate in the polyurethane foam forming composition / equivalent amount of active hydrogen in the polyurethane foam forming composition) × 100].

[0026] Examples of appropriate auxiliary agents included in the polyurethane foam forming composition include fillers, crosslinking agents, antioxidants, moisture absorbers, and colorants.

[0027] Examples of fillers include aluminum hydroxide, talc, calcium carbonate, and clay. Examples of crosslinking agents include polyhydric alcohols such as glycerin, butanetetraol, and polyoxypropylene glycol, as well as diethanolamine and polyamines.

[0028] Examples of antioxidants include phenolic antioxidants, amine antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants. Examples of moisture absorbents include synthetic zeolite, silica powder, alumina powder, lithium hydroxide powder, and barium hydroxide powder.

[0029] Polyurethane foam forming compositions are foamed when a foaming agent is added. Examples of foaming agents include chemical foaming agents, physical foaming agents, and foam-forming gases. Chemical and physical foaming agents are mainly used in mold foaming and slab foaming, while foam-forming gases are mainly used in mechanical floss foaming.

[0030] Chemical blowing agents are substances that generate foaming gas through heating or reaction, and one example is water, which reacts with polyisocyanate to produce carbon dioxide. Physical foaming agents are substances that produce bubbles by reducing their solubility through reduced pressure or heating, or by vaporizing and expanding liquid substances at or near room temperature due to the heat of reaction. Examples include methylene chlorides, chlorofluorocarbons, hydrocarbons, and carbon dioxide. The foaming gas is a gas that causes foaming (foaming) when mixing polyurethane foam-forming compositions, and examples include dry air and nitrogen.

[0031] The molding density of polyurethane foam (JIS K7222:2005) is 30-500 kg / m³. 3 Preferably, 40-400 kg / m 3 More preferably, 50-300 kg / m 3 This is even more preferable. If the molding density of the polyurethane foam is too low or too high, when it is compressed between two objects when used as a sealant, the adhesion to both objects will be reduced, resulting in a decrease in sealing performance.

[0032] When used as a sealing material, the polyurethane foam of the present invention is formed, for example, into a string-like or frame-like shape (including annular) by punching or the like, and is attached to the fitting portion between the main body and the lid of, for example, an electronic device housing (case), and is compressed and used between the main body and the lid. [Examples]

[0033] Using the following raw materials, polyurethane foams were formed by the mechanical froth foaming method from the polyurethane foam-forming compositions having the formulations of each of the examples and each of the comparative examples shown in FIGS. 2 and 3. The isocyanate index in the polyurethane foam-forming composition used was 103. Specifically, a foaming gas (air) as a foaming agent was mixed into the polyurethane foam-forming composition at a mixing ratio of 35% by volume, and after mixing for 2 minutes with a hand mixer to cause foaming, the mixture was filled into a plastic cup with a capacity of 220 cm 3 The upper end of the plastic cup was scraped off, and the cup weight (weight per cup) was measured, and in this state, it was cured to form a polyurethane foam in the plastic cup.

[0034] For each of the examples and each of the comparative examples, the foam density (kg / m 3 ) was calculated using the formula of [cup weight / capacity of plastic cup (220 cm 3 )]. The foaming property (foaming ability) in each of the examples and each of the comparative examples was determined. The foaming property is the foam content (foaming ability) immediately after mixing of the polyurethane foam-forming composition into which the foaming gas has been mixed. It indicates that when the foam density is low, the foaming property (foaming ability) is high, and conversely, when the foam density is high, the foaming property (foaming ability) is low, and it is affected by the foam stabilizer. The determination of the foaming property was marked as "〇" when the foam density was less than 500 kg / m 3 , "△" when it was less than 500 to 700 kg / m 3 , and "×" when it was 700 kg / m 3 or more.

[0035] For each of the examples and each of the comparative examples, the cured polyurethane foam was taken out of the plastic cup, and the molding density (kg / m 3 ) was measured based on JIS K7222:2005, and the value of [molding density ÷ foam density] was calculated. If the value of [molded density ÷ foam density] is greater than 1, it indicates that the air bubbles generated by mixing decreased during curing, resulting in an increase in the density of the polyurethane foam. Conversely, if the value of [molded density ÷ foam density] is 1 or less, it indicates that the air bubbles generated by mixing did not decrease, or even increased, during curing, resulting in no change or a decrease in the density of the polyurethane foam. Furthermore, the cell size (μm) of the polyurethane foam for each example and comparative example was measured in accordance with JIS K6400-1 (Annex).

[0036] The retention of the cellular structure formed by mixing the polyurethane foam-forming composition was judged using the following criteria to determine whether the polyurethane foam was formed while maintaining the cellular structure. The cellular structure was maintained by the cellular structure. A good retention rating ("○") was given when the cellular structure was 1.0 or less and the cell size was less than 300 μm (indicated as "<300 μm"). Poor retention was given in all other cases ("×"). In Figure 3, "2000<" means greater than 2000 μm.

[0037] If the retention rate is "○", it indicates that the state of the bubbles (cell structure) formed by mixing the polyurethane foam forming composition is sufficiently maintained until the polyurethane foam forming composition hardens, resulting in the formation of a dense cellular polyurethane foam. On the other hand, if the retention rate is "×", it indicates that the bubbles formed by mixing the polyurethane foam forming composition decrease due to coalescence, merging, release, rupture, etc., during the hardening period of the polyurethane foam forming composition, resulting in the inability to obtain a dense cellular polyurethane foam.

[0038] Furthermore, the amount of silicone component (ppm) was measured for the polyurethane foam of each example and comparative example. The measurement method involved placing Soxhlet extract (acetone) into a glass tube, placing it in a thermal desorption apparatus, and measuring the generated gas by gas chromatography (GC) for each polyurethane foam of each example and comparative example.

[0039] The ingredients used are as follows: • Polyether polyol 1: Molecular weight 3000, number of functional groups 2, hydroxyl value (OHV) 38 mg KOH / g, product name: Actcol ED-37B, manufactured by Mitsui Chemicals SKC Polyurethane Co., Ltd. • Polyether polyol 2: Molecular weight 600, number of functional groups 3, hydroxyl value (OHV) 281 mg KOH / g, product name: GP-600, manufactured by Sanyo Chemical Industries, Ltd. • Polyether polyol 3: Dipropylene glycol, hydroxyl value (OHV) 837 mg KOH / g, manufactured by AGC Inc.

[0040] • Polyester polyol 1: Polycaprolactone diol, molecular weight 530, number of functional groups 2, hydroxyl value (OHV) 212 mg KOH / g, product name: Praxel 205, manufactured by Daicel Chemicals, Inc. • Polyester polyol 2: Polycarbonate diol, molecular weight 500, number of functional groups 2, hydroxyl value (OHV) 224 mgKOH / g, product name: PH-50, manufactured by Ube Industries, Ltd.

[0041] • Silicone-based foam stabilizer: Block copolymer of dimethylsiloxane and polyether, product name: SZ-1952, manufactured by Dow-Toray. • Cardanol-based surfactant 1: ethylene oxide 7 molar addition, product name: GX-5166, manufactured by Cardwright Corporation. • Cardanol-based surfactant 2: ethylene oxide 9 molars added, product name: GX-5167, manufactured by Cardwright Corporation. • Cardanol-based surfactant 3: 12 moles of ethylene oxide added, product name: GX-5170, manufactured by Cardwright Corporation.

[0042] • Catalyst: Organic acid salt type, Product name: FIN-P1, manufactured by Nippon Chemical Industrial Co., Ltd. • Filler: Aluminum hydroxide, product name: CW-325LV, manufactured by Sumitomo Chemical Co., Ltd. • Polyisocyanate: Polymeric isocyanate prepolymer, NCO%; 25%, Product name; FoamLite 3700B, manufactured by BASF INOAC Polyurethane Corporation.

[0043] The following describes each example and each comparative example. <Example using polyether polyols> • Comparative Example 1 Comparative Example 1 is an example in which a polyether polyol is used as the polyol and neither a silicone-based foam stabilizer nor a cardanol-based surfactant is included. The results for Comparative Example 1 showed no foaming (foaming), foaming ability "×", retention ability "×", and silicone component amount "not detected", indicating that a polyurethane foam with a good foaming (foaming) state could not be obtained.

[0044] Examples 1 to 3 Examples 1 to 3 use a polyether polyol as the polyol, vary the type of cardanol-based surfactant used as the foam stabilizer, and use an amount of 3.0 parts by weight per 100 parts by weight of polyol, without including a silicone-based foam stabilizer. The results for Examples 1 to 3 showed foaming ability "○", retention ability "○", and silicone component amount "not detected", indicating a good foaming state and no problems with silicone contamination.

[0045] • Comparative Example 2 Comparative Example 2 uses a polyether polyol as the polyol, and the amount of silicone-based foam stabilizer added is 3.0 parts by weight per 100 parts by weight of polyol, and does not contain a cardanol-based surfactant. The results for Comparative Example 2 were "○" for foaming ability, "○" for foam retention, and "206 ppm" for silicone component content, indicating a good foaming state, but there is a problem with silicone contamination.

[0046] Examples 4 to 6 Examples 4 to 6 use a polyether polyol as the polyol, vary the type of cardanol-based surfactant used as the foam stabilizer, and use an amount of 6.0 parts by weight per 100 parts by weight of polyol, without including a silicone-based foam stabilizer. The results for Examples 4 to 6 showed foaming ability "○", retention ability "○", and silicone component amount "not detected", indicating a good foaming state and no problems with silicone contamination.

[0047] • Comparative Example 3 Comparative Example 3 is an example in which a polyether polyol is used as the polyol, the amount of silicone-based foam stabilizer is 6.0 parts by weight per 100 parts by weight of polyol, and no cardanol-based surfactant is included. The results for Comparative Example 3 were "○" for foaming ability, "○" for foam retention, and "423 ppm" for silicone component content, indicating a good foaming state, but there is a problem with silicone contamination.

[0048] Examples 7 to 9 Examples 7 to 9 use a polyether polyol as the polyol, vary the type of cardanol-based surfactant used as the foam stabilizer, and use an amount of 9.0 parts by weight per 100 parts by weight of polyol, without including a silicone-based foam stabilizer. The results for Examples 7 to 9 showed foaming ability "○", retention ability "○", and silicone component amount "not detected", indicating a good foaming state and no problems with silicone contamination.

[0049] • Comparative Example 4 Comparative Example 4 is an example in which a polyether polyol is used as the polyol, the amount of silicone-based foam stabilizer is 9.0 parts by weight per 100 parts by weight of polyol, and no cardanol-based surfactant is included. The results for Comparative Example 4 showed foaming ability "○", foam retention "○", and silicone component content "588 ppm", indicating a good foaming state, but there is a problem with silicone contamination.

[0050] <Examples of mixed use of polyether polyol and polyester polyol> Examples 10-12 Examples 10 to 12 use polyether polyols 1, 2, and 3 and polyester polyol 1 in varying mixing ratios, and the amount of cardanol-based surfactant 1 used as a foam stabilizer is 6.0 parts by weight per 100 parts by weight of polyol, and do not contain a silicone-based foam stabilizer. The results for Examples 10 to 12 showed foaming ability "○", retention ability "○", and silicone component amount "not detected", indicating a good foaming state and no problems with silicone contamination.

[0051] • Comparative Example 5 Comparative Example 5 is an example in which polyol is used in a mixture of polyether polyols 1, 2, and 3 and polyester polyol 1, and does not contain either a silicone-based foam stabilizer or a cardanol-based surfactant. The results for Comparative Example 5 showed foaming ability "○", foam retention "×", and silicone component amount "not detected", indicating that a good polyurethane foam could not be obtained.

[0052] Examples 13 to 15 Examples 13 to 15 use polyether polyols 1, 2, and 3 and polyester polyol 2 in varying mixing ratios, and the amount of cardanol-based surfactant 1 used as a foam stabilizer is 6.0 parts by weight per 100 parts by weight of polyol, and do not contain a silicone-based foam stabilizer. The results for Examples 13 to 15 showed foaming ability "○", retention ability "○", and silicone component amount "not detected", indicating a good foaming state and no problems with silicone contamination.

[0053] • Comparative Example 6 Comparative Example 6 is an example in which polyol is used in a mixture of polyether polyols 1, 2, and 3 and polyester polyol 2, and does not contain either a silicone-based foam stabilizer or a cardanol-based surfactant. The results for Comparative Example 6 were "△" for foaming ability, "×" for foam retention, and "not detected" for silicone component content, indicating that a good polyurethane foam could not be obtained.

[0054] Thus, the polyurethane foam of the present invention uses a cardanol-based surfactant as a foam stabilizer and does not require a silicone-based foam stabilizer. As a result, no silicone components are detected, there is no risk of silicone contamination, and it is suitable as a sealing material for electronic devices and the like. It should be noted that the present invention is not limited to the examples provided and can be modified without departing from the spirit of the invention. For example, even if a cardanol-based surfactant is used as a foam stabilizer, and a small amount of a silicone-based foam stabilizer is used in addition, specifically in a smaller amount than the cardanol-based surfactant, it is possible to produce a polyurethane foam with low silicone contamination.

Claims

1. A polyurethane foam formed from a polyurethane foam-forming composition containing a cardanol-based surfactant, which is cardanol to which ethylene oxide or propylene oxide is added, as a foam stabilizer, but which does not contain a silicone-based foam stabilizer.

2. The polyurethane foam according to claim 1, characterized in that the cardanol-based surfactant is contained in 1 to 12 parts by weight per 100 parts by weight of polyol in the polyurethane foam forming composition.

3. A method for producing polyurethane foam, characterized by mixing a polyurethane foam-forming composition containing a cardanol-based surfactant as a foam stabilizer but not a silicone-based foam stabilizer, and allowing it to react and cure.

4. The method for producing polyurethane foam according to claim 3, characterized in that the cardanol-based surfactant is contained in 1 to 12 parts by weight per 100 parts by weight of polyol in the polyurethane foam forming composition.

5. A sealing material formed from polyurethane foam according to claim 1 or 2.

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