Non-foam polyurethane resin and method for producing the same

Abstract

To provide a non-foam polyurethane resin which prevents drip without using a flame retardant and a drip prevention agent, and is excellent in flame retardancy.SOLUTION: A non-foam polyurethane resin is obtained while containing at least polyol (A), polyisocyanate (B) and a polymerization initiator (C) as raw materials, wherein a part or all of the polyol (A) is polyester polyol (A-1) obtained by esterification reaction of a polyhydric alcohol component and a polyhydric carboxylic acid component, a polyhydric carboxylic acid having a double bond as a carboxylic acid component used in the polyester polyol (A-1) is contained in the polyester polyol (A-1) so as to have double bond concentration of 3 to 16 mass%, and a foaming agent is not contained.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a non-foamed polyurethane resin, and in particular to a flame-retardant non-foamed polyurethane resin that does not contain a blowing agent. [Background technology]

[0002] There are many types of synthetic polymers, including polyethylene, polypropylene, styrene resins, polyvinyl chloride, polyurethane, epoxy resins, acrylic resins, and fluororesins, and they are used in a wide range of fields. Among them, polyurethanes are used for a wide range of purposes, including as resins for paints and inks, packaging and cushioning materials, insulation materials, synthetic leather, and textiles and clothing.

[0003] Polyurethane is a polymer with urethane bonds obtained by the polymerization reaction of polyol and polyisocyanate. By changing the type of polyol and isocyanate, it is possible to create a material that has a wide range of properties, from rubber-like flexibility to the hard and strong properties of rubber tires.

[0004] There are two types of polyurethane: foamed polyurethane (polyurethane foam) and non-foamed polyurethane resin. Polyurethane foam is used as a porous material by adding a foaming agent during the polymerization reaction to generate bubbles throughout the polymer, and the air layer provides insulation and cushioning properties, making it used as packaging, cushioning material, and insulation. On the other hand, non-foamed polyurethane resin is useful in applications that make use of the excellent flexibility, high elasticity, and high stretchability of polyurethane resin.

[0005] Polyurethanes are classified into thermoplastic polyurethanes and thermosetting polyurethanes. Thermoplastic polyurethanes can be melted and molded, making them suitable for mass production processes such as injection molding. For example, they are used in soles of sports shoes and ski boots, snorkels, fins, automobile parts, watch bands, grips of bicycles and golf clubs, camera bodies, etc. However, they melt when heated, so their heat resistance is low. On the other hand, thermosetting polyurethanes are also called thermosetting urethane elastomers, and do not melt even when heated, have excellent elasticity and stretchability, and are used in fields where durability and heat resistance are required in addition to these properties. For example, they are used in rolls such as papermaking rolls and printing rollers, belts such as conveyor belts, and parts of electronic devices, taking advantage of their excellent elasticity.

[0006] On the other hand, the performance required for resin components such as general elastomers, coating agents, adhesives, and waterproofing materials varies depending on the part where they are used, and includes water resistance, weather resistance, strength, heat resistance, flame retardancy, etc. In recent years in particular, heat resistance and flame retardancy have become important in every field, and in order to improve the heat resistance and flame retardancy, it is necessary to use many flame retardants (Patent Document 1).

[0007] As flame retardants, halogen-based or phosphorus-based flame retardants are often used (Patent Document 2), or there is a method of increasing flame retardancy by adding halogen to polyether polyol itself as a resin raw material (Patent Document 3). However, halogen-based flame retardants such as chlorine-based and bromine-based flame retardants may generate harmful gases such as dioxins during fire or incineration. Phosphorus may also cause water pollution due to the phosphoric acid contained in the combustion ash. Therefore, methods to reduce or not use these are required from the perspective of danger and environmental load.

[0008] When a metal hydroxide-based flame retardant is added (Patent Document 4), a large amount of flame retardant, 30 mass% or more of the total mass of the resin, must be added in order to meet the flame retardancy standard. On the other hand, adding a large amount of flame retardant causes a problem that the mechanical properties such as elongation, hardness, and breaking strength of the resin molded product are reduced. For this reason, it is difficult to achieve both high flame retardancy and good mechanical properties.

[0009] In general, in the case of polyurethane foam, even if a large amount of additives such as flame retardants are added, there are few problems with physical properties such as heat insulation effect and cushioning. However, in the case of non-foamed urethane resin, for example, non-foamed polyurethane used in parts that contact high-temperature parts such as heat generating parts of mobile batteries and precision machines and partitions of engine rooms, flame retardancy is required, and there is a concern that adding a large amount of flame retardant will cause a decrease in mechanical properties, resulting in the necessary strength as a component being no longer met or long-term durability being lost. In particular, when used as a thermosetting non-foamed polyurethane, adding a large amount of additives such as flame retardants will drastically decrease the mechanical properties required for the properties, such as elasticity, elongation, hardness, and breaking strength, so there is a demand for a resin composition that can ensure flame retardancy and does not impair mechanical properties even without adding flame retardants.

[0010] There are also examples where flame retardant effects are obtained by including polyhydric phenol compounds (tannin compounds), saccharide compounds (monosaccharides, disaccharides, oligosaccharides and polysaccharides), fatty acid compounds (organic carboxylates), polysaccharides having acidic functional groups (Patent Document 5), etc. as flame retardants (Patent Document 6). However, the method of using such a large amount of flame retardants to increase heat resistance and flame retardancy has problems in all aspects, including danger and cost performance. Thus, in general, the mechanical properties deteriorate when there is a large amount of flame retardant. In addition, there are problems such as a decrease in glass transition point, poor weight loss upon heating, and bleeding out, so a formulation that does not require the use of flame retardants is required.

[0011] The heat resistance and flame retardancy of such resin components can be judged by whether they meet the UL-94 standard, which is globally recognized as a grade of flame retardancy for plastic materials. When plastic materials are burned according to UL-94, the melted resin drips. The dripping resin creates new burning surfaces one after another, and those that do not have self-extinguishing properties will burn out to the end. Therefore, it is a known technology that a flame retardant needs to be added to give the resin self-extinguishing properties, but the present invention makes it possible to increase the heat resistance and flame retardancy of the main agent of non-foamed polyurethane resin without the need for additives.

[0012] Patent Document 7 discloses a non-foamed or foamed polyurethane having a concentration of vinyl polymerizable functional groups in the resin of 0.05 to 6 mmol / g as a flame-retardant resin. However, the vinyl polymerizable functional groups are terminal vinyl groups, specifically acrylic acid esters, which are different from the carboxylic acids having double bonds of the present invention, and the content is low at 0.05 to 6 mmol / g, and if it exceeds 6 mmol / g, brittleness will occur.

[0013] Patent Document 8 discloses a polyurethane resin obtained from polyester polyol and polyisocyanate as a resin having excellent solvent resistance and hydrolysis resistance, and discloses a combination of an unsaturated polycarboxylic acid and a saturated polycarboxylic acid as a polycarboxylic acid forming the polyester polyol. A composition is disclosed in which the molar ratio of the unsaturated polycarboxylic acid to the saturated polycarboxylic acid is 5 to 45 mol %. It is said that this composition promotes crosslinking when forming a polyurethane molded product, imparting solvent resistance and hydrolysis resistance, but there is no description of flame retardancy. It is also said that if the unsaturated polycarboxylic acid exceeds 45 mol %, they will polymerize with each other during the esterification reaction, gelling, and the production of the polyester polyol will become extremely unstable.

[0014] Patent Document 9 discloses a polyurethane foam containing at least a polyisocyanate, a polyol, a blowing agent, a catalyst, a surfactant, and a polymerization inhibitor, in which fumaric acid and / or maleic acid is used as the carboxylic acid component in polyester polyol (A) in an amount of 10 mol % or more based on the total carboxylic acid components in polyester polyol (A). However, this example is an example of a polyurethane foam, and contains a blowing agent in the composition, and has a different application from the present invention, a different production method (a foaming and curing production method) and a different composition. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] JP 2020-41111 A [Patent Document 2] Japanese Patent Application Publication No. 2-199162 [Patent Document 3] JP 2022-111064 A [Patent Document 4] Japanese Patent Application Publication No. 7-145288 [Patent Document 5] JP 2023-11097 A [Patent Document 6] JP 2006-77215 A [Patent Document 7] JP 2010-031242 A [Patent Document 8] JP 2012-017356 A [Patent Document 9] JP 2016-148014 A Summary of the Invention [Problem to be solved by the invention]

[0016] Therefore, an object of the present invention is to provide a technology for preventing dripping during combustion of a non-foamed polyurethane resin and improving the flame retardancy without using a flame retardant or anti-drip agent. [Means for solving the problem]

[0017] As a result of intensive research, the present inventors discovered that the above problems can be solved by using a polyester polyol having specific structural features as a polyol for producing a non-foamed polyurethane resin, which led to the completion of the following present invention.

[0018] The first invention is a non-foamed polyurethane resin obtained from at least a polyol (A), a polyisocyanate (B), and a polymerization inhibitor (C) as raw materials, The non-foamed polyurethane resin is characterized in that a part or all of the polyol (A) is a polyester polyol (A-1) obtained by an esterification reaction between a polyhydric alcohol component and a polycarboxylic acid component, the carboxylic acid component used in the polyester polyol (A-1) contains a polycarboxylic acid having a double bond such that the double bond concentration is 3 to 16 mass% relative to the polyester polyol (A-1), the polycarboxylic acid having a double bond in the polycarboxylic acid exceeds 45 mol% relative to the total polycarboxylic acid, and no foaming agent is contained.

[0019] A second invention resides in the non-foamed polyurethane resin according to the first invention, characterized in that the polycarboxylic acid having a double bond is contained in the polyester polyol (A-1) so that the double bond concentration is 5 to 12 mass %.

[0020] A third invention resides in the non-foamed polyurethane resin according to the first invention, characterized in that the non-foamed polyurethane resin does not contain a flame retardant or the content of the flame retardant is 0.05 mass% or less based on the polyester polyol (A-1).

[0021] A fourth invention resides in the non-foamed polyurethane resin according to the second invention, characterized in that the non-foamed polyurethane resin does not contain a flame retardant or the content of the flame retardant is 0.05 mass% or less based on the polyester polyol (A-1).

[0022] A fifth invention resides in the non-foamed polyurethane resin according to the first invention, characterized in that the non-foamed polyurethane resin further contains a phosphorus compound as a catalyst deactivator for the esterification catalyst, and the content of the phosphorus compound relative to the polyester polyol (A-1) is 0.0001 mass % or more and 0.05 mass % or less.

[0023] A sixth invention resides in the non-foamed polyurethane resin according to the second invention, further comprising a phosphorus compound as a catalyst deactivator for the esterification catalyst, the content of which is 0.0001 mass % or more and 0.05 mass % or less relative to the polyester polyol (A-1).

[0024] A seventh invention resides in the non-foamed polyurethane resin according to any one of the first to sixth inventions, wherein the polyester polyol (A-1) has a functionality of 1.0 to 4.0.

[0025] An eighth invention resides in the non-foamed polyurethane resin according to any one of the first to sixth inventions, characterized in that the non-foamed polyurethane resin contains, as the polymerization inhibitor (C), at least 1,4-naphthoquinone and / or hydroquinone in an amount of 1 to 10,000 ppm by mass relative to the polyester polyol (A-1).

[0026] A ninth aspect of the present invention resides in a method for producing a non-foamed polyurethane molded product, comprising using the non-foamed polyurethane resin according to any one of the first to sixth aspects and a thermal radical polymerization initiator. Effect of the Invention

[0027] According to the method for producing a non-foamed polyurethane resin of the present invention, it is possible to prevent dripping during combustion of the non-foamed polyurethane resin and improve the flame retardancy without using a flame retardant / anti-drip agent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention will be described in detail below.

[0029] (Non-foaming polyurethane resin) The present invention relates to a non-foamed polyurethane resin obtained from raw materials containing at least a polyol (A), a polyisocyanate (B) and a polymerization inhibitor (C), wherein a part or all of the polyol (A) is a polyester polyol (A-1) obtained by an esterification reaction of a polyhydric alcohol component and a polycarboxylic acid component, the carboxylic acid component used in the polyester polyol (A-1) contains a polycarboxylic acid having a double bond such that the double bond concentration is 3 to 16 mass% relative to the polyester polyol (A-1), and the non-foamed polyurethane resin does not contain a foaming agent.

[0030] Each component constituting the non-foamed polyurethane resin will now be described.

[0031] (Polyol (A)) The polyol (A) used in the non-foamed polyurethane resin of the present invention contains polyester polyol (A-1) as an essential component, and may contain other polyols such as polyether polyol. Examples of polyols that can be used other than polyester polyol (A-1) include known polyether polyols, polymer polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and vinyl monomer modified polyols having a hydroxyl value of 20 to 800 mg KOH / g and a functionality of 1.0 to 8.0. Commercially available products can be used for all of these. These may be used alone or in combination of two or more.

[0032] The polyester polyol (A-1) is obtained by an esterification reaction between a carboxylic acid component and an alcohol component. In the present invention, the polyester polyol (A-1) made of a carboxylic acid having a double bond, such as fumaric acid, is used as an essential component.

[0033] The double bond concentration is calculated from the composition ratio and indicates the amount of C=C (molecular weight 24) contained in the polyester polyol in mass %. The double bond represented by C=C is not a double bond contained in an aromatic, but an independent double bond. The polycarboxylic acid having this double bond is used so that the double bond is 1 to 20 mass%, preferably 3 to 16 mass%, and more preferably 5 to 12 mass% relative to the polyester polyol (A-1). If the double bond is less than 1 mass%, the effect of improving flame retardancy is reduced. On the other hand, there is no particular upper limit for the double bond concentration, and all of the polycarboxylic acid components may be double bond-containing polycarboxylic acids. That is, the entire amount of the polyester polyol used as the polyol may be polyester polyol (A-1).

[0034] Examples of polyvalent carboxylic acids having a double bond include fumaric acid, maleic acid, citraconic acid, mesaconic acid, itaconic acid, etc., and two or more of these may be used in combination. Among these, preferred carboxylic acids are fumaric acid and maleic acid.

[0035] Other polycarboxylic acid components that can be used in combination with the polycarboxylic acid having a double bond can be known carboxylic acids that are generally used in the manufacture of polyester polyols.Specific examples include phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, HET acid, dimer acid, malic acid, and citric acid.Each of these may be used as a derivative such as an acid anhydride or methyl ester, or two or more of them may be used in combination.

[0036] Among these other polycarboxylic acids, from the viewpoint of improving the flame retardancy of the non-foamed polyurethane resin, it is preferable to use phthalic acid, terephthalic acid, and isophthalic acid. Also, from the viewpoint of moldability of the non-foamed polyurethane resin, it is preferable to use succinic acid and / or adipic acid in order to reduce the viscosity of the polyester polyol (A-1). The amount of the other polycarboxylic acids used is less than 55 mol%, preferably less than 50 mol%, based on the total polycarboxylic acid components. That is, it is preferable to use more than 45 mol% of the polycarboxylic acid having a double bond, more preferably 50 mol% or more, based on the total polycarboxylic acid components.

[0037] The alcohol component of the polyester polyol (A-1) can be a known alcohol generally used in the production of polyester polyol.Specific examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, polyoxyethylene / oxypropylene copolymer glycol, long-chain polyether polyols such as polytetramethylene ether glycol, glycerin, trimethylolpropane, pentaerythritol, etc.Two or more of these may be used in combination.

[0038] Among these alcohols, it is particularly preferable to use ethylene glycol and / or diethylene glycol. The amount of ethylene glycol and / or diethylene glycol used is usually 20 mol% or more, preferably 30 mol% or more, and more preferably 40 mol% or more, based on the alcohol component of the polyester polyol (A-1). If the amount of ethylene glycol and / or diethylene glycol is less than 20 mol%, the effect of improving flame retardancy is reduced. On the other hand, there is no particular upper limit for the amount of ethylene glycol and / or diethylene glycol, and the entire alcohol component may be ethylene glycol and / or diethylene glycol.

[0039] The hydroxyl value of the polyester polyol (A-1) is usually in the range of 30 to 500 mgKOH / g, preferably 40 to 480 mgKOH / g, and more preferably 50 to 450 mgKOH / g. If the hydroxyl value is less than 30 mgKOH / g, the mechanical strength of the resulting non-foamed polyurethane resin may decrease. On the other hand, if the hydroxyl value is more than 500 mgKOH / g, the molecular weight distribution may be such that there is a large amount of unreacted alcohol, which may cause brittleness or deterioration of adhesiveness.

[0040] The viscosity of the polyester polyol (A-1) at 25°C is usually 80,000 mPa·s or less, preferably 75,000 mPa·s or less, and more preferably 70,000 mPa·s or less. If it is higher than 80,000 mPa·s, handling may be difficult. On the other hand, there is no particular lower limit for the viscosity.

[0041] In addition, as a method for reducing the viscosity of polyester polyol (A-1), monohydric alcohols such as methanol, ethanol, isopropanol, and 2-ethylhexanol can be used in combination. However, when using these monohydric alcohols, it is important that the hydroxyl value and the number of functional groups do not deviate from the above range. Furthermore, in the production of polyester polyol, the monohydric alcohol may be distilled out of the reaction system, which may deteriorate the yield, or may adversely affect the strength and flame retardancy of the non-foamed polyurethane resin using the obtained polyester polyol, so it is preferable to use it within a range that does not cause practical problems.

[0042] The average functionality of the polyester polyol (A-1) is usually in the range of 1.0 to 4.0, preferably 1.2 to 3.8, and more preferably 1.5 to 3.5. If the average functionality is less than 1.0, adverse effects such as a decrease in the mechanical strength and dimensional stability of the non-foamed polyurethane resin may occur. On the other hand, if it is more than 4.0, the viscosity of the polyester polyol increases, which may cause problems.

[0043] In the production of polyester polyol (A-1), an esterification catalyst is usually used as a catalyst. As the esterification catalyst, an acid catalyst is generally used. Specifically, orthotitanate esters such as tetraisopropyl titanate and tetra-n-butyl titanate, tin compounds such as diethyltin oxide and dibutyltin oxide, and metal compounds such as zinc oxide are used. In addition, Bronsted acids such as paratoluenesulfonic acid may be used.

[0044] The amount of the esterification catalyst used is usually 0.1% by mass or less, preferably 0.07% by mass or less, and more preferably 0.05% by mass or less, based on the total charged weight of the alcohol component and the polyvalent carboxylic acid component. However, when molding a non-foamed polyurethane resin, the esterification catalyst may promote the urethanization reaction, making it impossible to ensure the molding time, so the reaction may be carried out without using the esterification catalyst, or the esterification catalyst may be deactivated after the reaction or removed by purification or the like.

[0045] In the production of polyester polyol (A-1), the end point of the esterification reaction is usually determined by the amount of unreacted carboxyl groups of the polycarboxylic acid used. In order to improve the finish of the non-foamed polyurethane resin, it is preferable that the amount of unreacted polycarboxylic acid, i.e., the acid value, is as low as possible. The acid value of the polyester polyol (A-1) of the present invention is usually 3 mg KOH / g or less, preferably 2 mg KOH / g or less, and more preferably 1 mg KOH / g or less. On the other hand, there is no particular lower limit, but it is about 0.1 mg KOH / g considering the reaction conditions and reaction time.

[0046] In the production of the polyester polyol (A-1), the reaction conditions of the esterification reaction, such as the reaction temperature and reaction pressure, are not particularly limited, and known methods can be used.

[0047] Examples of polyols other than polyester polyols used as the polyol (A) for the non-foamed polyurethane resin of the present invention include polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polyhexamethylene glycol. Examples of polymer polyols include those obtained by graft polymerizing acrylonitrile, styrene, and the like with polyether polyols. Examples of polycarbonate polyols include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, and poly(1,4-cyclohexanedimethylene carbonate) diol.

[0048] The amount of polyester polyol (A-1) used is usually 20 parts by weight or more, preferably 50 parts by weight or more, more preferably 80 parts by weight or more, based on 100 parts by weight of the total polyol (A). If the amount used is less than 20 parts by weight, the flame retardancy of the non-foamed polyurethane resin decreases. On the other hand, there is no particular upper limit to the amount used, and it is most preferable that the total amount of polyol (A) is polyester polyol (A-1).

[0049] (Polyisocyanate (B)) The polyisocyanate (B) is not particularly limited as long as it is a compound having two or more isocyanate groups in one molecule. For example, aliphatic, alicyclic, aromatic polyisocyanates or modified products thereof can be mentioned. Specifically, hexamethylene diisocyanate, isophorone diisocyanate, or polyisocyanate can be mentioned, and polyisocyanates can be tolylene diisocyanate, diphenylmethane diisocyanate, or polyphenylene polymethylene polyisocyanate, etc., and further, modified products such as carbodiimide modified products and prepolymers thereof can also be used.

[0050] The preferred polyisocyanate is an aromatic polyisocyanate or a modified product thereof, and particularly preferred are diphenylmethane diisocyanate, polyphenylene polymethylene polyisocyanate, tolylene diisocyanate, and modified products thereof. These may be used in combination of two or more. The polyphenylene polymethylene polyisocyanate preferably has an isocyanate group content of usually 25 to 35 mass% and a viscosity of usually 500 mPa·s (25°C) or less.

[0051] In the non-foamed polyurethane resin of the present invention, the isocyanate index of the non-foamed polyurethane resin is [(Total number of moles of isocyanate groups) / (Total number of moles of active hydrogen groups)×100] and is usually 80 to 400, preferably 90 to 350, and more preferably 100 to 300. If the isocyanate index is less than 80, the resulting non-foamed polyurethane resin may not have sufficient strength, while if it exceeds 400, the resulting non-foamed polyurethane resin may become highly brittle and have reduced strength, which is undesirable.

[0052] (Polymerization inhibitor (C)) When producing a non-foamed polyurethane resin using polyester polyol (A-1), a polymerization inhibitor is added in advance. This is to prevent the storage stability from deteriorating due to the polymerization of polyester polyol (A-1). As the polymerization inhibitor, a known polymerization inhibitor can be used. Specifically, hydroquinones such as hydroquinone, methylhydroquinone, 2-methylhydroquinone, and t-butylhydroquinone, benzoquinones such as p-benzoquinone and methyl-p-benzoquinone, naphthoquinones such as 1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone, naphthoquinones such as 1,4-naphthohydroquinone and 2-methyl-1,4-naphthohydroquinone, catechols such as catechol and t-butylcatechol, phenols such as 2,6-di-t-butyl-4-methylphenol, 4-methoxyphenol, and cresol, N-oxyls such as 1-oxyl-2,2,6,6-tetramethylpiperidin-4-ol, and other known polymerization inhibitors such as phenothiazine, ferdazyl, and α,α-diphenyl-β-picrylhydrazyl may be used in combination of two or more of these polymerization inhibitors.

[0053] In particular, hydroquinone and 1,4-naphthoquinone are preferred, and it is particularly preferred to use these two in combination.

[0054] The amount of the polymerization inhibitor used is usually 1 to 10,000 ppm by mass, preferably 5 to 5,000 ppm by mass, and more preferably 10 to 1,000 ppm by mass, based on the polyester polyol (A-1). If the amount used is less than 1 ppm by mass, the effect of preventing polymerization is small and storage stability is deteriorated. On the other hand, the amount may exceed 10,000 ppm by mass, but from the viewpoint of preventing polymerization, 1,000 ppm by mass is sufficient to obtain the effect.

[0055] The polymerization inhibitor may be added together with the carboxylic acid and alcohol before the esterification reaction, or may be added successively during the esterification reaction, or may be added after the esterification reaction is completed. The polymerization inhibitor may also be added in two or more portions, such as before the reaction and after the reaction. Considering that some polymerization proceeds during the esterification reaction, it is most preferable to add the polymerization inhibitor before the start of the esterification reaction.

[0056] (Phosphorus Compounds as Catalyst Deactivators) When molding a non-foamed polyurethane resin, the esterification catalyst contained in the polyester polyol (A-1) may accelerate curing, making it difficult to ensure the molding time. Therefore, it is desirable to add a phosphorus compound as a catalyst deactivator to suppress or deactivate the activity of the esterification catalyst. In particular, in the case of a titanium-based catalyst, the activity of the catalyst can be suppressed and the molding time can be ensured by treating it with a phosphorus compound such as phosphoric acid, a phosphoric acid ester, phosphorous acid, or a phosphorous acid ester. Specifically, preferred examples of phosphorous acid or phosphoric acid, or mono- or diesters thereof, include phosphorous acid, phosphoric acid, dimethyl phosphite, diethyl phosphite, diisopropyl phosphite, di-n-butyl phosphite, diisobutyl phosphite, di-n-ethylhexyl phosphite, dilauryl phosphite, dioleyl phosphite, distearyl phosphite, diphenyl phosphite, monomethyl phosphite, monoethyl phosphite, monoisopropyl phosphite, mono-n-butyl phosphite, monoisobutyl phosphite, mono-n-ethylhexyl phosphite, monolauryl phosphite, phosphorous ... Examples of the phosphorus compounds include monooleyl acid, monostearyl phosphate, monophenyl phosphite, dimethyl phosphate, diethyl phosphate, diisopropyl phosphate, di-n-butyl phosphate, diisobutyl phosphate, di-n-ethylhexyl phosphate, dilauryl phosphate, dioleyl phosphate, distearyl phosphate, diphenyl phosphate, monomethyl phosphate, monoethyl phosphate, monoisopropyl phosphate, mono-n-butyl phosphate, monoisobutyl phosphate, mono-n-ethylhexyl phosphate, monolauryl phosphate, monooleyl phosphate, monostearyl phosphate, and monophenyl phosphate. Among the above phosphorus compounds, phosphoric acid is particularly preferred.

[0057] The amount of the phosphorus compound added to the non-foamed polyurethane resin of the present invention is preferably 0.0001% by mass or more and 0.05% by mass or less based on the polyester polyol (A-1). If it is less than 0.0001% by mass, the activity of the esterification catalyst cannot be suppressed, and even if it is added in excess of 0.05% by mass, the effect of suppressing the activity of the esterification catalyst remains unchanged, and conversely, there is a possibility that the strength and molding of the polyurethane resin will be impaired.

[0058] (Plasticizer) The non-foamed polyurethane resin of the present invention may further contain a plasticizer to improve the flexibility of the molded product. Examples of the plasticizer include conventional plasticizers such as phthalic acid esters, phosphate esters, trimellitic acid esters, pyromellitic acid esters, fatty acid esters, epoxy plasticizers, polyether plasticizers, liquid rubber, and non-aromatic paraffin oil.

[0059] Since the non-foamed polyurethane resin of the present invention has sufficient flame retardancy, there is no need to add a flame retardant. However, even if a flame retardant is added or an additive compound that is added for another purpose and may also act as a flame retardant is added, the amount of the flame retardant added is preferably 0.05 mass % or less, and particularly preferably 0.0001 mass % or less.

[0060] Examples of flame retardants that are commonly added include phosphorus- and halogen-containing organic compounds, bromine- or chlorine-containing organic compounds, ammonium polyphosphate, aluminum hydroxide, antimony oxide, and reactive flame retardants.

[0061] (Other additives) The non-foamed polyurethane resin of the present invention may contain conventional additives, such as stabilizers (weather resistance stabilizers, antioxidants, heat stabilizers, light stabilizers, etc.), fillers, lubricants, colorants, solvents, etc. These additives may be used alone or in combination of two or more.

[0062] (Method of manufacturing non-foamed polyurethane moldings) Next, a method for producing a non-foamed polyurethane molded product using the non-foamed polyurethane resin of the present invention will be described.

[0063] The method for producing a non-foamed polyurethane molded product of the present invention is to mix a polyol containing the polyester polyol of the present invention with a polyisocyanate and harden it. In practice, phosphoric acid and, if necessary, plasticizers and other additives are added to the polyol, and a polyol liquid is prepared by heating to 80°C and dehydrating under reduced pressure. The polyol liquid heated to 80°C is added to a vacuum mixer, and the polyisocyanate, also heated to 80°C, is stirred vigorously under reduced pressure, and finally degassed and poured into a mold. For example, a 200mm x 200mm x 3mm mold made of SUS is used, and preheated to a hardening temperature. After pouring the liquid into the mold, it is hardened at 100°C for 8 hours.

[0064] In addition, in the present invention, a urethane catalyst can be used for the purpose of promoting the reaction during curing. The urethane catalyst can be an amine catalyst or a metal catalyst, and both are used in non-foamed polyurethane. Specifically, for example, amine-based compounds such as tertiary amines such as triethylamine, N-ethylmorpholine, triethylenediamine, and diazabicycloundecene, organic tin compounds such as dioctyltin dilaurate, trimethyltin laurate, dibutyltin dilaurate, and dibutyltin di-2-ethylhexanoate, organic titanium compounds, and organic lead compounds such as lead octylate can be mentioned. In the case of an amine catalyst, an amine forms a complex with an isocyanate, and an active hydrogen compound such as an alcohol reacts with this to form a urethane bond. In the case of a metal compound, a complex is formed between an isocyanate, an alcohol, and a metal catalyst, and the metal catalyst is removed from the complex to form a urethane compound.

[0065] In the production of the non-foamed polyurethane molding of the present invention, a thermal radical polymerization initiator is further added. As the thermal radical polymerization initiator, a general thermal radical polymerization initiator can be used, for example, peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, diisopropyl peroxycarbonate, di-2-ethylhexyl peroxycarbonate, tert-butyl peroxypiperate, and azo compounds such as 1,1'-azobiscyclohexane-1-carbonitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis-(methylisobutyrate), α,α-azobis-(isobutyronitrile), and 4,4'-azobis-(4-cyanovaleric acid) can be mentioned.

[0066] This thermal radical polymerization initiator is intended to radically polymerize the polycarboxylic acid having a double bond contained in the polyester polyol (A-1) of the present invention during molding of the non-foamed polyurethane molded product of the present invention. It is believed that the flame retardancy of the non-foamed polyurethane molded product is exhibited by radical polymerization of the double bond group of the polycarboxylic acid having a double bond.

[0067] It is preferable to mix the thermal radical polymerization initiator, urethane catalyst, and other additives in advance with the polyol liquid and then mix them with the isocyanate, but in some cases they may be mixed with the isocyanate, or when mixing the polyol liquid and the isocyanate, they may be directly added to the vacuum mixer. When producing a non-foamed polyurethane molded product, the polyol liquid and the isocyanate may be adjusted to 10 to 100°C in some cases, and the curing temperature may be adjusted to 80 to 150°C.

[0068] There are no particular limitations on additives and auxiliaries other than those described above, so long as they do not impair the effects of the present invention. Any additives and auxiliaries used for the purpose of improving physical properties or operability, etc., can be used as long as they do not have a significant adverse effect. EXAMPLES

[0069] Hereinafter, specific embodiments of the present invention will be described in further detail with reference to examples. However, the present invention is not limited to these examples as long as it does not depart from the gist of the present invention.

[0070] (Synthesis of polyester polyol (A-1)) Polyester polyol (A-1) was synthesized by a known method. The obtained polyester polyols (A-1) were designated as polyester polyols A2 to A5 and A7 to A9, and the compositions of the raw material carboxylic acid components and alcohol components, polymerization inhibitor, acid value, hydroxyl value, viscosity, and water content are shown in Tables 1 and 2. The physical property evaluation methods of polyester polyol (A-1) are shown in Table 3.

[0071] [Table 1]

[0072] [Table 2]

[0073] [Table 3]

[0074] (Evaluation of non-foamed polyurethane resin) (UL-94 equivalent flame test) In the UL-94 standard test, which is globally recognized as a grading system for the flame resistance of plastic materials, test pieces cut to 150~175mm x 13mm were held horizontally, with the flame of a wingtip burner adjusted to approximately 40mm, and exposed to the flame for 10 seconds. After ignition, the test was continued until the fire self-extinguished, and a comparison was made of the weight loss rate and burning behavior (presence or absence of dripping, etc.) before and after the test.

[0075] (TG-DTA) Thermal weight loss analysis TG-DTA measurement was performed under the conditions shown in Table 4. [Table 4]

[0076] (Production of non-foamed polyurethane resin) Non-foamed polyurethane resins were synthesized by the method described above with the formulations shown in Tables 5 and 6. Test results equivalent to UL-94 and TG-DTA measurement results are also summarized in Tables 5 to 7. The isocyanate index of this example and comparative example is 105.

[0077] [Table 5]

[0078] As is clear from a comparison of Examples 1 and 2 with Comparative Example 1, Examples 1 and 2, which contain fumaric acid, a carboxylic acid having a double bond, in the polyester polyol and have a double bond concentration of 6.6 or 4.7, show a large amount of dripping in the UL-94 equivalent test in Comparative Example 1, which uses a polyester polyol that does not contain a carboxylic acid having a double bond, whereas Examples 1 and 2 prevent dripping and show a significantly improved survival rate after combustion.

[0079] [Table 6]

[0080] Furthermore, in Examples 3 and 4, in which the double bond concentrations in the polyester polyol were 5 and 12, respectively, the mass residual rates in the TG-DTA analysis of the weight loss when heated at 300°C for 20 minutes were significantly improved to 88% by mass and 91% by mass, respectively, compared to 84% by mass in Comparative Example 1.

[0081] [Table 7]

[0082] In Examples 5 and 6, the number of functional groups was increased, and in order to avoid high viscosity due to the increased number of functional groups, adipic acid was added in Example 5, and the molecular weight was reduced in Example 6, but neither showed dripping in the UL-94 equivalent test, and showed a high survival rate even after combustion. Comparative Example 2 did not use a carboxylic acid with a double bond, but used an aromatic carboxylic acid, which is generally said to have high heat resistance and flame retardancy, but a large amount of dripping occurred. Similarly, in Comparative Example 3, PPG, which is widely used, also dripped, and the residual rate of TG-DTA also decreased.

[0083] From the above results, the following points are mainly clear.

[0084] The non-foamed polyurethane resins of Examples 1 to 6 using the polyester polyol of the present invention did not drip in the UL-94 equivalent test and showed a high residual rate. On the other hand, the non-foamed polyurethane resins using polyols not using carboxylic acids having double bonds as in Comparative Examples 1 to 4 drip in the UL-94 equivalent test and the residual rate is low depending on the type. The TG-DTA also shows a similar tendency.

Claims

1. A non-foamed polyurethane resin obtained from at least a polyol (A), a polyisocyanate (B) and a polymerization inhibitor (C), The non-foamed polyurethane resin is characterized in that a part or all of the polyol (A) is a polyester polyol (A-1) obtained by an esterification reaction between a polyhydric alcohol component and a polycarboxylic acid component, the carboxylic acid component used in the polyester polyol (A-1) contains a polycarboxylic acid having a double bond such that the double bond concentration is 3 to 16 mass % relative to the polyester polyol (A-1), the polycarboxylic acid having a double bond in the polycarboxylic acid exceeds 45 mol % relative to the total polycarboxylic acid, and no foaming agent is contained.

2. The non-foamed polyurethane resin according to claim 1, characterized in that the polyvalent carboxylic acid having a double bond is contained in the polyester polyol (A-1) so that the double bond concentration is 5 to 12 mass%.

3. The non-foamed polyurethane resin according to claim 1, which does not contain a flame retardant or contains a flame retardant in an amount of 0.05 mass% or less based on the polyester polyol (A-1).

4. The non-foamed polyurethane resin according to claim 2, which does not contain a flame retardant or contains a flame retardant in an amount of 0.05 mass% or less based on the polyester polyol (A-1).

5. The non-foamed polyurethane resin according to claim 1, further comprising a phosphorus compound as a catalyst deactivator for the esterification catalyst, the content of which is 0.0001 mass% or more and 0.05 mass% or less based on the polyester polyol (A-1).

6. The non-foamed polyurethane resin according to claim 2, further comprising a phosphorus compound as a catalyst deactivator for the esterification catalyst, the content of which is 0.0001 mass% or more and 0.05 mass% or less based on the polyester polyol (A-1).

7. The non-foamed polyurethane resin according to any one of claims 1 to 6, wherein the polyester polyol (A-1) has a functionality of 1.0 to 4.

0.

8. The non-foamed polyurethane resin according to any one of claims 1 to 6, characterized in that it contains at least 1,4-naphthoquinone and / or hydroquinone as a polymerization inhibitor (C) in an amount of 1 to 10,000 ppm by mass relative to the polyester polyol (A-1).

9. A method for producing a non-foamed polyurethane molded product, comprising using the non-foamed polyurethane resin according to any one of claims 1 to 6 and a thermal radical polymerization initiator.

Images