JP2008094950A - Heat-resistant phenolic resin composition excellent in storage stability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant phenolic resin composition excellent in storage stability which is not accompanied by the change with time in the lowering of heat decomposition resistance and the like even on the storage (of molded articles) before and after curing. <P>SOLUTION: The phenolic resin composition having storage stability and excellent heat decomposition resistance having a resin remaining ratio after heating at 350&deg;C for 24 hours in the air of not less than 50 wt.% can be obtained by incorporating a borate into a general-purpose phenolic resin. Furthermore, by incorporating a combination of metal hydroxides such as an alkali metal hydroxide, an alkaline earth metal hydroxide, and aluminum hydroxide into the phenolic resin in addition to the above borate, the heat decomposition resistance can be further improved while maintaining storage stability. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a phenol resin composition, and more particularly, to a heat resistant phenol resin composition excellent in storage stability, in which heat decomposition resistance does not decrease with time.

  Phenolic resins have excellent heat resistance, and are widely used as plastic materials in fields requiring heat resistance as resins containing glass fibers and the like. However, with the development of technology, the demand for heat resistance has become more sophisticated, and there have been fields where the heat resistance of conventional phenolic resins is insufficient. Specifically, high heat resistance is required such that the residual resin ratio after 24 hours at 350 ° C. in air is 50% by weight or more. In the evaluation of thermogravimetric analysis, there is a possibility that the residual resin rate at a certain temperature shows a temporary value and does not match the environment at the time of actual use, and the residual resin rate evaluation (constant temperature durability test) is performed at a constant temperature. In this constant temperature endurance test, it seems that the test is generally performed for 20 to 40 minutes, and the evaluation with the resin residual ratio after 24 hours can be said to be extremely severe conditions.

  In order to improve the heat resistance of phenolic resins, phenolic resins in which various compounds are reacted or added later have been proposed. For example, a phenol resin composition in which an alkali metal hydroxide (see Patent Document 1), an alkaline earth metal hydroxide (see Patent Document 2), or the like is reacted with a phenol resin or added to the phenol resin, respectively. Or the phenol resin composition (refer patent document 3) which heat-melted the boric acid and the novolak-type phenol resin is proposed. Moreover, although it is not heat resistant, the phenol resin composition which mix | blended boric acid and sodium metaborate with an acid hardening agent with the resol type phenol resin as a flame retardant is also proposed (refer patent document 4).

  When a large amount of an alkali metal hydroxide is added to the phenol resin afterwards, a high degree of thermal decomposition is temporarily obtained, but as a result of studies by the present inventors, the thermal decomposition decreases with time. It became clear.

  In addition, the phenol resin composition using boric acid can improve the heat resistance and flame retardancy, but in order to obtain a higher degree of thermal decomposition, a large amount of boric acid is dissolved in a solvent such as methanol. It must be added to the resin. In this case, white powder boric acid is deposited before curing (in a state where boric acid is dissolved in the phenolic resin using methanol or the like) or after curing (molded product). If such precipitation of boric acid occurs before curing, the precipitation and volatilization of the additive will cause the need for re-dissolution, adverse effects on production equipment, etc. This causes a problem that the effect of the present application cannot be obtained due to a decrease in the thermal decomposition resistance of the molded product after curing. In addition, when boric acid is precipitated over time after curing, the heat decomposability deteriorates over time, and the molded product has a problem of poor appearance due to the precipitate.

  Furthermore, it has been clarified that the phenol resin to which an alkaline earth metal hydroxide is added afterwards has a lower effect of improving the heat decomposability at 350 ° C. in air than the above compound.

As described above, conventionally, phenolic resins whose thermal decomposition resistance is improved by post-addition have a problem that the thermal decomposition resistance decreases with time before curing (before molding) or after curing (molded product). It was.
JP 2005-239949 A JP-A-6-298888 JP-A-5-59257 Japanese Patent No. 3754166

  In view of the heat resistance required for phenolic resins as described above and the current state of heat-resistant phenolic resins, the present invention has a high resin residual rate of 50% by weight or more at high temperatures (350 ° C. in air for 24 hours). In addition to its excellent heat decomposability, the precipitation and volatilization of additives prior to curing can lead to deterioration in the handling and working environment during manufacturing, and the deterioration of the heat decomposability of molded products after curing. In addition, it is intended to provide a heat-decomposable phenolic resin composition having excellent storage stability that is not accompanied by a change over time, such as a decrease in heat-decomposability even during storage after storage (molded product). .

  The heat-resistant phenol resin according to the present invention comprises 10% by weight to 80% by weight of at least one borate based on the phenol resin.

  The second heat-resistant phenolic resin according to the present invention further contains a metal hydroxide in addition to the above.

  The borate is preferably at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts.

  The metal hydroxide is preferably at least one selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and aluminum hydroxide, and the content thereof is a phenol resin. The content is preferably 1 to 20% by weight.

  According to the present invention, a phenol resin composition excellent in storage stability and heat decomposability can be obtained by adding borate to a general-purpose phenol resin. Furthermore, in addition to the borate, a combination of a metal hydroxide such as an alkali metal hydroxide, an alkaline earth metal hydroxide, or aluminum hydroxide is added to the phenol resin to maintain storage stability. However, the thermal decomposition resistance can be further improved as compared with the case of adding borate alone. The phenol resin composition of the present invention has an excellent heat decomposability in which the residual resin ratio after heating at 350 ° C. for 24 hours in air is 50% by weight or more, and the heat decomposability does not decrease during storage It is a composition.

  In the present invention, various compounds are post-added to the phenol resin in a stage before curing in order to obtain a heat-decomposable phenol resin composition that does not require special reaction conditions. The phenol resin is obtained by reacting phenols and aldehydes in the presence of an acid or alkali catalyst, but the post-addition compound and the synthesis catalyst have different roles. Post-addition here refers to adding various compounds to a phenolic resin (liquid or solid without a normal temperature solvent) in a state before curing, and melt mixing or dissolving mixing. Some phenolic resins before curing exhibit solid or liquid properties at room temperature / no solvent. In the post-addition method in the present invention, after reacting phenols and aldehydes, a compound such as a borate or a metal hydroxide is added to a phenol resin before curing, followed by dry blending (mixing powders with a mixer). ), Melt mixing (kneading at a temperature higher than the softening point of the phenol resin), or dissolution mixing (mixing the phenol resin and the compound using a solvent). In the dissolution and mixing, the temperature is appropriately adjusted (15 to 50 ° C.) or the solvent is appropriately added and dissolved. The solvent is not particularly limited, and for example, water, alcohols (such as methanol), and ketones (such as acetone and methyl ethyl ketone) are preferable.

  The phenols constituting the phenol resin are not particularly limited, and examples thereof include alkylphenols (cresol, xylenol, etc.), polyhydric phenols (resorcinol, etc.), phenylphenol, aminophenol, and the like. Moreover, aldehydes are not specifically limited, Formaldehyde, paraformaldehyde, acetaldehyde, etc. are mentioned.

  The phenol resin may be either a resol type obtained by reacting phenols and aldehydes in the presence of an alkali catalyst or a novolak type obtained by reacting in the presence of an acid catalyst.

  The borate added to the phenol resin is not particularly limited, but preferably an alkali metal salt or an alkaline earth metal salt, more preferably sodium borate, lithium borate, potassium borate, or magnesium borate, More preferred are sodium metaborate, sodium tetraborate, and lithium metaborate. When these borates and the above phenol resin are mixed, the change in viscosity of the phenol resin is small, and a homogeneous phenol resin composition can be obtained, so that a high thermal decomposition resistance improvement effect can be obtained. The amount of borate added is preferably 10% by weight to 80% by weight with respect to the phenol resin. When the addition amount is less than 10% by weight, the effect of improving the thermal decomposition resistance is small, and when it exceeds 80% by weight, the moldability tends to be difficult. If the addition amount is 40% by weight or less, the moldability is improved, which is more preferable.

  Further, the metal hydroxide is not particularly limited, but alkali metal hydroxide, alkaline earth metal hydroxide, and aluminum hydroxide are preferable. By using these metal hydroxides, high thermal decomposition resistance can be imparted to the phenol resin composition. As the alkali metal hydroxide, sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferable. As the alkaline earth metal hydroxide, calcium hydroxide, magnesium hydroxide, and barium hydroxide are preferable. The addition amount of the metal hydroxide is preferably 1% by weight to 20% by weight and more preferably 1% by weight to 10% by weight with respect to the phenol resin. If it is less than 1% by weight, sufficient thermal decomposition resistance cannot be imparted, and the moldability gradually decreases as the addition amount increases, and if it exceeds 20% by weight, the curing reaction of the phenol resin proceeds and gelation occurs. Use as a molding material becomes difficult.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to these examples, and the type of phenol resin (the raw material species and the catalyst described in paragraph [0016] are described below). (Alkali or acid), raw material molar ratio (formaldehydes / phenols = 0.8 to 2.5)), types of borate and metal hydroxide, and their addition amount, etc. Is possible.

  In addition, prior to the description of the examples and comparative examples, the implemented evaluation method of the phenol resin composition is described below.

(Sample adjustment)
As a sample, the obtained phenol resin composition solution, a solution obtained by curing the solution at 180 ° C. for 30 minutes without containing a substrate such as glass fiber (hereinafter referred to as “cured product powder”). ) And the above solution are impregnated into a glass cloth, and laminated molded at 180 ° C. × 5 MPa × 30 minutes so as to have a thickness of 10 mm (hereinafter referred to as “laminated molded product”). Storage stability and thermal decomposition resistance were evaluated.

(Storage stability)
The phenol resin composition solution before curing, and the cured product powder and laminated molded product after curing are allowed to stand for 1 month at 25 ° C. and 60% RH, respectively, and the presence or absence of precipitation of the added compound is visually observed. confirmed.

(Heat-resistant decomposition)
(1) Residual Residual Ratio after Heating The cured product powder was placed in a hot air circulation drying oven set at 350 ° C. for 24 hours and evaluated by the residual resin ratio after heating. Furthermore, the storage stability of heat resistance was evaluated by comparing the resin residual ratio in a sample immediately after curing and a sample stored for 2 months at 25 ° C. and 60% RH after curing. Here, the resin residual ratio is as follows.
(Resin residual ratio after heating) = (weight after heating at 350 ° C. for 24 hours) / (initial weight before heating at 350 ° C.) × 100

(2) Whitening characteristics at the time of heating The presence or absence of whitening when the above-mentioned laminated molded product was exposed to a hot-air circulating drying oven set at 300 ° C, 350 ° C, and 400 ° C for 5 hours was visually confirmed.
Here, when a phenol resin molded product containing glass fiber or the like is heated in air at 300 ° C. or higher for a long time, oxidative decomposition proceeds from the surface layer, and the glass fiber or the like is exposed and appears white. In particular, in a molded article of a phenol resin containing a large amount of a metal salt or the like, whiteness becomes more noticeable because metal oxides remain in addition to glass fibers and the like. In the present invention, such a phenomenon is defined as whitening.
In addition, even in the case of a resin showing a good resin residual ratio in the above-described thermal decomposability evaluation for a phenolic resin alone, in a heating test of a molded product based on glass fiber that is a general actual use form, Some of the above-mentioned whitening phenomenon occurs and does not show good thermal decomposition resistance. Therefore, in addition to the evaluation of the thermal decomposition resistance of the phenol resin alone, as a representative example, the whitening characteristics during heating were evaluated as the evaluation of the thermal decomposition resistance of a molded article based on glass fiber.

(Example 1)
The resol type phenol resin uses phenol (P) and formaldehyde (F) as raw materials, its molar ratio F / P = 1.5, and NaOH as a synthesis catalyst, and is reacted for 30 minutes under reflux at 98 ° C. Water (from 37% formaldehyde aqueous solution and water from condensation reaction) and the synthesis catalyst were removed after the reaction. A phenol resin having a weight average molecular weight (polyethylene oxide equivalent, solvent: dimethylformamide) of 950 was prepared by gel filtration chromatography.
30 weight% of sodium tetraborate was melt | dissolved with respect to the said phenol resin, and the phenol resin composition was obtained.

(Example 2)
A phenol resin composition was obtained by post-adding 30% by weight of lithium metaborate to the phenol resin produced in the same manner as in Example 1.

(Example 3)
A phenol resin composition was obtained by post-adding 40% by weight of sodium metaborate to the phenol resin produced in the same manner as in Example 1.

Example 4
A phenol resin composition was obtained by post-adding 30% by weight of sodium metaborate to the phenol resin produced in the same manner as in Example 1.

(Example 5)
A phenol resin composition was obtained by post-adding 10% by weight of sodium metaborate to the phenol resin produced in the same manner as in Example 1.

(Example 6)
A phenol resin composition was obtained by post-adding 30% by weight of sodium metaborate and 10% by weight of sodium hydroxide to the phenol resin produced in the same manner as in Example 1.

(Example 7)
A phenol resin composition was obtained by post-adding 30% by weight of sodium metaborate and 10% by weight of calcium hydroxide to the phenol resin produced in the same manner as in Example 1.

(Example 8)
A phenol resin composition was obtained by post-adding 10% by weight of sodium metaborate and 10% by weight of calcium hydroxide to the phenol resin produced in the same manner as in Example 1.

Example 9
A phenol resin composition was obtained by post-adding 30% by weight of sodium metaborate and 1% by weight of calcium hydroxide to the phenol resin produced in the same manner as in Example 1.

(Example 10)
To the phenolic resin produced in the same manner as in Example 1, 30% by weight of sodium tetraborate and 10% by weight of sodium hydroxide were added afterwards to obtain a phenolic resin composition.

(Example 11)
A phenol resin composition was obtained by post-adding 30% by weight of lithium metaborate and 10% by weight of aluminum hydroxide to the phenol resin produced in the same manner as in Example 1.

(Example 12)
The production method of the novolac type phenol resin is as follows.
Phenol (P) and formaldehyde (F) were added so that the molar ratio was F / P = 0.8, and lactic acid as a synthesis catalyst was added to this solution, and reacted at 98 ° C. under reflux for 30 minutes. . After removing water, the reaction was completed by heating to 180 ° C. After cooling, the mixture was pulverized and 10% by weight of hexamine was mixed by dry blending to obtain a novolac type phenol resin. A phenol resin having a weight average molecular weight (polyethylene oxide equivalent, solvent: dimethylformamide) of 1280 by gel filtration chromatography was obtained.
The novolac-type phenol resin was dissolved in methanol, and sodium metaborate was dissolved at 30% by weight with respect to the phenol resin to obtain a phenol resin composition.

(Comparative Example 1)
A phenol resin was prepared in the same manner as in Example 1, but no post-addition was performed.

(Comparative Example 2)
To the phenolic resin produced in the same manner as in Example 1, 10% by weight of sodium hydroxide was added afterwards to obtain a phenolic resin composition.

(Comparative Example 3)
A phenol resin composition was obtained by post-adding 20% by weight of potassium hydroxide to the phenol resin produced in the same manner as in Example 1.

(Comparative Example 4)
A phenol resin composition was obtained by post-adding 15% by weight of calcium hydroxide to the phenol resin produced in the same manner as in Example 1.

(Comparative Example 5)
A phenol resin composition was obtained by post-adding 15% by weight of boric acid to the phenol resin produced in the same manner as in Example 1. In addition, since boric acid was dissolved in phenol, methanol was used as a solvent. This is because in order to dissolve with water, it is necessary to maintain a temperature of 80 ° C. or higher, and the curing of the phenol resin is promoted. Moreover, it is difficult to dissolve boric acid in a phenol resin in an amount of more than 15% by weight.

(Comparative Example 6)
A phenol resin composition was obtained by post-adding 0.3% by weight of boric acid and 3.2% by weight of sodium metaborate to the phenol resin produced in the same manner as in Example 1.

(Comparative Example 7)
A phenol resin composition was obtained by post-adding 7% by weight of sodium metaborate to the phenol resin produced in the same manner as in Example 1.

  In the above examples and comparative examples, sodium tetraborate, lithium metaborate, sodium metaborate, sodium hydroxide, calcium hydroxide, and aluminum hydroxide are dissolved in the phenolic resin, so water is used as a solvent. Post-added to phenolic resin.

  About the phenol resin composition obtained in the said Examples 1-12 and Comparative Examples 1-7, storage stability, the resin residual rate after a heating, and the whitening characteristic at the time of a heating were evaluated, and the result was shown in Table 1. . In addition, about the comparative example 5, the sample used for thermal decomposition resistance evaluation shall remove the white powder (boric acid) which precipitated during storage.

From the above, the present invention has high thermal decomposition resistance (resin residual ratio of 50 wt% or more after heating in air at 350 ° C. for 24 hours) by post-adding a borate exhibiting alkalinity in an aqueous solution to a phenol resin. The phenol resin composition has almost no change in the residual ratio of the resin during storage and has no change in properties during storage. Further, in addition to the borate, the molded article using the phenol resin composition in which the above-mentioned various metal hydroxides are used in combination does not whiten even in an extremely severe heating environment.
Therefore, the present invention is a phenol resin composition suitable as a highly heat-resistant resin that is industrially required, and does not require special reaction conditions or special raw materials. Since it can be manufactured by dissolving the additive, it is possible to provide a heat-resistant phenol resin composition having excellent storage stability at low cost.

Claims (5)

  A heat-resistant phenolic resin composition comprising 10% to 80% by weight of at least one borate in a phenolic resin, based on the phenolic resin.   The heat-resistant phenol resin composition according to claim 1, further comprising a metal hydroxide.   The heat-resistant phenol resin composition according to claim 1 or 2, wherein the borate is at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts.   The heat-resistant phenol resin according to any one of claims 2 to 3, wherein the metal hydroxide is at least one selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and aluminum hydroxide. Composition. The heat-resistant phenol resin composition according to any one of claims 2 to 4, wherein the metal hydroxide is contained in an amount of 1 to 20% by weight based on the phenol resin.