Phenolic resin composition

Abstract

To provide a phenol resin composition which extremely reduces contents of both free phenol and free aldehyde, has high water solubility, and is excellent in handleability or workability.SOLUTION: A phenol resin composition contains a water-soluble resol type phenol resin, an amino acid or its salt, in which the amino acid is a water-soluble amino acid having a molecular weight of 89 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a phenolic resin composition containing a water-soluble resol-type phenolic resin. More specifically, it relates to a phenolic resin composition with reduced formaldehyde and phenol contents.

Background Art

[0002] Phenolic resins are typical thermosetting resins used in many fields due to the heat resistance and high mechanical strength of their cured products. Phenolic resins are used, for example, by being impregnated or coated on various substrates or as binders for various organic and inorganic substrates. Phenolic resins are roughly classified into novolak-type phenolic resins that are heated and cured by adding a curing agent such as hexamethylenetetramine and resol-type phenolic resins that are heated and cured alone, and are used appropriately according to properties, uses, purposes, etc.

[0003] Among these phenolic resins, for applications that require ammonia-free or for cases where a solvent-free is necessary for environmental compatibility and improvement of the working environment, resol-type phenolic resins with high hydrophilicity are often used in applications where they are used in the form of an aqueous solution or emulsion. Water-soluble resol resins are used, for example, as binders for abrasive papers. Resol resins are excellent in abrasive grain holding power and heat resistance, and high grindability can be obtained.

[0004] However, this resol type phenolic resin contains unreacted phenols and unreacted aldehydes, which are substances not desirable from the viewpoints of protecting the atmospheric environment and the human environment. In order to obtain a resol type phenolic resin with a reduced formaldehyde content, an excess amount of phenols may be reacted with aldehydes. However, the resol type phenolic resin obtained by using an excess amount of phenols contains a large amount of unreacted phenols, resulting in poor curability. Furthermore, the mechanical strength of the resulting cured product may not reach the level required by the market, which may cause restrictions in its applications. In addition, the resol type phenolic resin obtained by using an excess amount of phenols contains a large amount of unreacted phenols, so it is not preferable to use it from the aspects of the environment and labor safety and hygiene.

[0005] As a technique for solving the above problems, Patent Document 1 describes a method for producing a resol resin capable of reducing the amount of unreacted monomers such as formaldehyde and phenol. Patent Document 1 describes a method for producing a liquid resin showing a free phenol level of 0.5% or less by blending 0.1 to 0.5 mol of glycine per 1 mol of starting phenol with a phenol-formaldehyde condensate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the method described in Patent Document 1 still has room for further improvement in achieving both the improvement of the water solubility of the obtained phenolic resin and the reduction of free formaldehyde and free phenol.

Means for Solving the Problems

[0008] The present invention has been made in view of the above problems, and aims to provide a phenolic resin composition in which the contents of both free phenol and free aldehyde, which are unreacted monomers, are reduced, and which has high water solubility, and thus excellent handleability or workability.

[0009] According to the present invention, a water-soluble resol-type phenolic resin, amino Acid salt and, are included, the amino acid Salt is a water-soluble amino acid having a molecular weight of 89 or more Salt of is, a phenolic resin composition is provided.

Effects of the Invention

[0010] According to the present invention, a phenolic resin composition in which the contents of both free phenol and free aldehyde are very much reduced, and which has high water solubility, and thus excellent handleability or workability is provided.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described. In this specification, the notation "a~b" in the description of a numerical range means "a or more and b or less" unless otherwise specified. For example, "5~90 mass%" means "5 mass% or more and 90 mass% or less".

[0012] (Phenolic Resin Composition) The phenolic resin composition of this embodiment contains a water-soluble resol-type phenolic resin and an amino acid or a salt thereof. In this embodiment, the amino acid is a water-soluble amino acid having a molecular weight of 89 or more.

[0013] The phenolic resin composition of this embodiment contains a water-soluble resol-type phenolic resin and a water-soluble amino acid having a molecular weight of 89 or more or a salt thereof. By containing an amino acid or a salt thereof, the amount of free aldehyde and free phenol, which are unreacted residual monomers inevitably contained in the water-soluble resol-type phenolic resin, is reduced in the phenolic resin composition of this embodiment. Therefore, the environmental load and the load on the human body are reduced. Although the reason why the amount of free aldehyde and free phenol is reduced by the amino acid or a salt thereof is not necessarily clear, it is considered that free aldehyde and free phenol exist as non-volatile compounds or inactive compounds because the amino acid reacts or interacts with the free aldehyde and free phenol in the phenolic resin composition.

[0014] In addition, the phenolic resin composition of this embodiment has improved stability over time by containing an amino acid or a salt thereof. Here, the stability over time of the phenolic resin composition means that the change over time in the properties of the resin composition is small. The change over time in the properties of the resin composition includes that the phenolic resin contained in the resin composition has a higher molecular weight and the resin composition has a higher viscosity. The pH of the phenolic resin composition of this embodiment is Neutral region maintained, so that the increase in the molecular weight of the resol-type phenolic resin contained in the resin composition and the further polymerization reaction between unreacted free formaldehydes and free phenol are Inhibition suppressed, and almost no or no increase in the viscosity of the phenolic resin and change in the properties of the resin composition occur. Hereinafter, the components incorporated into the phenolic resin composition of this embodiment will be described in detail.

[0015] (Water-soluble resol-type phenolic resin) The water-soluble resol-type phenolic resin used in the phenolic resin composition of this embodiment is a resin obtained by reacting phenols and aldehydes in a reaction solvent under a basic catalyst under predetermined conditions described below.

[0016] Phenols used for the synthesis of the water-soluble resol-type phenol resin used in this embodiment include phenol; cresols such as o-cresol, m-cresol, and p-cresol; ethylphenols such as o-ethylphenol, m-ethylphenol, and p-ethylphenol; butylphenols such as isopropylphenol, butylphenol, and p-tert-butylphenol; alkylphenols such as p-tert-amylphenol, p-octylphenol, p-nonylphenol, and p-cumylphenol; halogenated phenols such as fluorophenol, chlorophenol, bromophenol, and iodophenol; monovalent phenol substituents such as p-phenylphenol, aminophenol, nitrophenol, dinitrophenol, and trinitrophenol; and monovalent phenols such as 1-naphthol and 2-naphthol; polyhydric phenols such as resorcin, alkylresorcin, pyrogallol, catechol, alkylcatechol, hydroquinone, alkylhydroquinone, phloroglucin, bisphenol A, bisphenol F, bisphenol S, and dihydroxynaphthalene. These may be used alone or in combination of two or more.

[0017] Aldehydes used for the synthesis of the water-soluble resol-type phenol resin used in this embodiment include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butylaldehyde, caproaldehyde, allyl aldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, etc. These may be used alone or in combination of two or more. Also, it is possible to use precursors of these aldehydes or solutions of these aldehydes. Among them, from the viewpoint of production cost, it is preferable to use an aqueous formaldehyde solution.

[0018] Examples of the basic catalyst used for the synthesis of the water-soluble resol type phenol resin used in this embodiment include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; carbonates such as sodium carbonate and calcium carbonate; oxides such as lime; sulfites such as sodium sulfite; phosphates such as sodium phosphate; and amines such as ammonia, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, hexamethylenetetramine, and pyridine.

[0019] Water is generally used as the reaction solvent for the synthesis of the water-soluble resol type phenol resin used in this embodiment, but an organic solvent may also be used. Specific examples of such organic solvents include alcohols, ketones, aromatics, etc. Specific examples of alcohols include methanol, ethanol, propyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, etc. Specific examples of ketones include acetone, methyl ethyl ketone, etc. Specific examples of aromatics include toluene, xylene, etc.

[0020] Examples of the form of the resol type phenol resin include solid, aqueous solution, solvent solution, and aqueous dispersion. When an organic solvent is used as the reaction solvent for the synthesis of the water-soluble resol type phenol resin, the organic solvent is removed from the reaction solution containing the reaction product by known means such as extraction and drying before use.

[0021] The resol-type phenolic resin used in this embodiment is prepared by charging phenols (P) and aldehydes (F) into a reaction kettle at a compounding molar ratio (F / P) of 0.8 or more, preferably 0.8 or more and 3.0 or less, more preferably 1.0 or more and 2.8 or less, and even more preferably 1.2 or more and 2.5 or less, and further adding the above-mentioned basic catalyst as a polymerization catalyst, and performing reflux for an appropriate time (for example, 3 to 6 hours). When the compounding molar ratio (F / P) of phenols (P) and aldehydes (F) is less than 0.8, the weight-average molecular weight of the resulting water-soluble resol-type phenolic resin is small and the heat resistance may be inferior. Also, when the compounding molar ratio (F / P) of phenols (P) and aldehydes (F) exceeds 3.0, gelation of the resin tends to progress during the reaction, so the reaction efficiency decreases, and an insoluble-in-water high-molecular-weight resol-type phenolic resin is produced, which is not preferable. The reaction temperature is, for example, 40°C to 120°C, preferably 60°C to 100°C. Thereby, gelation can be suppressed and a water-soluble resol-type phenolic resin having the target molecular weight can be obtained. The weight-average molecular weight of the water-soluble resol-type phenolic resin is preferably 250 to 3000, more preferably 300 to 2000. The resol-type phenolic resin having a molecular weight in the above range has water solubility and high heat resistance.

[0022] (Amino acid) The amino acid compounded in the phenolic resin composition of this embodiment is not particularly limited as long as it has a molecular weight of 89 or more and is water-soluble. Examples include neutral amino acids such as alanine, valine, and serine; acidic amino acids such as glutamine; and basic amino acids such as asparagine. The amino acid may be in the form of a salt, and examples of the amino acid salt include sodium salts and potassium salts of amino acids. The amino acid or its salt may be used alone or in combination of two or more.

[0023] Among them, preferred amino acids and their salts include aspartic acid and sodium aspartate. By using such amino acids, the pH of the resulting phenolic resin composition can be maintained at neutral, and high water solubility can be maintained.

[0024] (Method for producing phenolic resin composition) The phenolic resin composition of this embodiment can be obtained by dissolving a water-soluble resol-type phenolic resin and an amino acid component in water by known means to form an aqueous solution, or by adding an amino acid during the synthesis process of the above water-soluble resol-type phenolic resin.

[0025] The compounding amount of the amino acid or its salt is, for example, 0.1 to 30% by mass, preferably 0.5 to 25% by mass, more preferably 1 to 20% by mass, based on the water-soluble resol-type phenolic resin. By compounding the amino acid or its salt within the above range, the free aldehydes and free phenols remaining in the water-soluble resol-type phenolic resin can be reduced.

[0026] The resin composition of this embodiment is provided as an aqueous solution with a solid content of 10% by mass or more and 80% by mass or less. The solid content of the resin composition of this embodiment can be adjusted according to the use of the resin composition by adjusting the amount of water as the solvent. For example, when the resin composition of this embodiment is used as an adhesive for a friction material, the solid content is preferably 50 to 80% by mass. Thereby, the viscosity of the resulting resin composition becomes appropriate for application to the friction base material, and sufficient bonding strength for use as a friction material can be obtained. When the resin composition of this embodiment is used for impregnating a base material, the solid content is preferably 10 to 70% by mass. Thereby, a resin composition having excellent handleability and excellent impregnation properties is obtained, and thus a high-strength / high-quality molded product can be produced with excellent production efficiency.

[0027] The phenolic resin composition of this embodiment has a content of unreacted free phenols reduced to 1% by mass or less, preferably 0.8% by mass or less, more preferably 0.6% by mass or less, based on the entire phenolic resin composition.

[0028] Also, the phenolic resin composition of this embodiment has a content of unreacted free aldehydes reduced to 1% by mass or less, preferably 0.8% by mass or less, more preferably 0.6% by mass or less, based on the entire phenolic resin composition.

[0029] The pH of the phenolic resin composition of this embodiment is close to neutral, for example, 6 to 8, preferably 6.5 to 7.8, more preferably 6.8 to 7.5. Such a pH is achieved by the presence of an amino acid in the phenolic resin composition. The phenolic resin composition of this embodiment has excellent stability over time by having a pH within the above range.

[0030] The embodiments of the present invention have been described above, but these are examples of the present invention, and various configurations other than the above can also be adopted.

Examples

[0031] Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0032] (Example 1) To a reactor equipped with a stirrer, a reflux condenser, and a thermometer, 1000 parts by weight of phenol, 1638 parts by weight of a 37% aqueous formalin solution (F / P molar ratio = 1.9), and 30 parts by weight of sodium hydroxide were added, and the mixture was reacted at 90°C for 70 minutes. After adding 500 parts by weight of water thereto, 75 parts by weight of alanine was added at 60°C and dissolved to obtain a resin composition. The obtained resin composition was transparent, had a solid content of 48%, a pH of 7.4, and a water dilutability of 2.6 times at 25°C. The amount of alanine in the resin composition calculated from the usage amounts of the respective components was 5% by mass based on the total solid content of the resin composition. Also, this resin composition had a free phenol amount of 0.9% by mass as measured using gas chromatography and a free formaldehyde amount of 0.3% by mass as measured by titration.

[0033] (Example 2) A resin composition was obtained by synthesizing in the same manner as in Example 1 except that the alanine in Example 1 was changed to aspartic acid. The obtained resin composition was transparent, had a solid content of 48%, had a pH of 7.0, and was 2.3 times dilutable with water at 25°C. The amount of aspartic acid in the resin composition calculated from the usage amounts of the respective components was 5% by mass based on the total solid content of the resin composition. Also, this resin composition had a free phenol amount of 0.9% by mass as measured using gas chromatography and a free formaldehyde amount of 0.2% by mass as measured by titration.

[0034] (Example 3) A resin composition was obtained by synthesizing in the same manner as in Example 1 except that the alanine in Example 1 was changed to sodium aspartate. The obtained resin composition was transparent, had a solid content of 48%, had a pH of 7.5, and was more than 20 times dilutable with water at 25°C. The amount of sodium aspartate in the resin composition calculated from the usage amounts of the respective components was 5% by mass based on the total solid content of the resin composition. Also, this resin composition had a free phenol amount of 0.8% by mass as measured using gas chromatography and a free formaldehyde amount of 0.3% by mass as measured by titration.

[0035] (Example 4) A resin composition was obtained by synthesizing in the same manner as in Example 3 except that the sodium aspartate in Example 3 was changed to 15 parts by weight. The obtained resin composition was transparent, had a solid content of 47%, had a pH of 7.6, and was 10 times dilutable with water at 25°C.

[0036] The amount of sodium aspartate in the resin composition calculated from the usage amounts of the respective components was 1% by mass based on the total solid content of the resin composition. Also, in this resin composition, the amount of free phenol measured using gas chromatography was 1.0% by mass, and the amount of free formaldehyde measured by titration was 0.4% by mass. (Example 5) A resin composition was obtained in the same manner as in Example 3, except that the amount of sodium aspartate in Example 3 was changed to 220 parts by weight. The obtained resin composition was transparent, had a solid content of 50%, had a pH of 7.0, and was dilutable with water 20 times or more at 25°C. The amount of sodium aspartate in the resin composition calculated from the usage amounts of the respective components was 15% by mass based on the total solid content of the resin composition. Also, in this resin composition, the amount of free phenol measured using gas chromatography was 0.7% by mass, and the amount of free formaldehyde measured by titration was 0.2% by mass.

[0037] (Comparative Example 1) A resin composition was obtained in the same manner as in Example 1 without adding alanine in Example 1. The obtained resin composition was transparent, had a solid content of 49%, had a pH of 8.9, and was dilutable with water 1.8 times at 25°C. In this resin composition, the amount of free phenol measured using gas chromatography was 1.6% by mass, and the amount of free formaldehyde measured by titration was 1.0% by mass.

[0038] The results are summarized in Table 1 below.

[0039]

Table 1

[0040] In the phenolic resin compositions of the examples containing amino acids, the amounts of free phenol and free formaldehyde contained as unreacted monomers in the resin composition were reduced.

Claims

Claim 1 A water-soluble resol type phenol resin and, an amino acid salt, and comprising, wherein the amino acid salt is a salt of a water-soluble amino acid having a molecular weight of 89 or more, a phenolic resin composition. Claim 2 The phenolic resin composition according to claim 1, wherein the amino acid salt is at least one selected from aspartate and glutamate. Claim 3 The phenolic resin composition according to claim 1 or 2, wherein the amino acid salt is in an amount of 0.1% by mass or more and 30% by mass or less based on the total solid content of the phenolic resin composition.

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