JPH0432846B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-soluble resol type phenolic resin which has a large resin solid content retention during high temperature curing and which provides a cured product with excellent flexibility. Phenol resin generally forms a dense three-dimensional structure after curing, and has excellent heat resistance, abrasion resistance, mechanical strength,
It has excellent characteristics such as dimensional stability, electrical insulation, acid resistance, and low flammability, so it is used in large quantities in a wide variety of applications. However, in the production of water-soluble resol type phenolic resins, there is a limit to the resin formation reaction in order to maintain water solubility. For this reason, the resin formation reaction is often inevitably terminated when a large amount of free phenol, saligenin, etc. still remain. The higher the content of free phenol and saligenin, the more volatile components there are during high-temperature curing, and the lower the resin solids yield.
There are also many problems in terms of resource conservation and cost reduction. Furthermore, the cured product of ordinary phenolic resins is hard and has poor flexibility, which is often a drawback. As a result of intensive research on improving the properties of water-soluble resol type phenolic resin, the inventors found that
By modifying water-soluble resol type phenolic resin with polyhydric alcohols during the resin formation reaction, the degree of condensation can be increased, thus creating a new modified resol resin that completely overcomes all of the above-mentioned drawbacks. I came to the conclusion. Since the modified resol resin according to the present invention has a high degree of condensation, the content of low molecular weight substances such as free phenol and saligenin is small, so the resin solid content retention during high temperature curing is extremely high. This modified resol resin has excellent characteristics such as not being brittle when it is used as a binder to bind and harden a base material, and is extremely flexible. Furthermore, although this was an unexpected effect, the modified resol resin according to the present invention also has favorable properties such as a light hue of the cured product and good transparency. Due to such effects, it is thought that the uses of the modified resol resin according to the present invention will expand. Furthermore, as mentioned above, since the resin solid content yield is high, practical problems such as environmental hygiene, pollution prevention, resource saving, and cost reduction can be solved. The production method of the present invention basically involves reacting phenols, aldehydes, and polyhydric alcohols to obtain a water-soluble modified resol resin. The phenols used in the modified resol resin according to the present invention include phenol, cresol, xylenol, ethylphenol, propylphenol, propenylphenol, catechol, resorcinol,
Examples include hydroquinone, and the practice of the present invention also includes by-products produced when producing these phenols. Next, as aldehydes, formaldehyde, acetaldehyde, etc., and aldehyde generating substances such as trioxane, polyoxymethylene, etc. are used. Basic catalysts for reacting phenols and aldehydes include alkali metal oxides, hydroxides, carbonates, alkaline earth metal oxides, hydroxides, ammonia, triethylamine, triethanolamine, etc. It is one or more compounds selected from amines. The polyhydric alcohol used in the modified resol resin according to the present invention has 2 to 2 alcoholic hydroxyl groups.
It is 9. That is, diols such as ethylene glycol, propylene glycol, butylene glycol, hexanediol, heptanediol, diethylene glycol, dipropylene glycol, triethylene glycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, propanetriol, butanetriol, hexanetriol, etc. triols,
These include erythrites such as pentaerythritol, pentites such as adonite, hexites such as sorbitol and mannitrate, and polyhydric alcohols obtained by reducing other monosaccharides. The number of parts of polyhydric alcohol added according to the present invention is:
The amount is 3 to 80 parts by weight, preferably 5 to 60 parts by weight, based on 100 parts by weight of phenols. The modified resol resin according to the present invention has an average molecular weight n when the portion of the resol resin excluding the solvent is measured by high performance liquid chromatography.
150 to 400, and the content of a phenol mononuclear compound (a compound in which at least one methylol group is added to a phenol) as determined by the same measurement is 60% by weight or less of this portion. Among these ranges, the average molecular weight n of the relevant portion is 180 ~
300 Furthermore, when the content of the mononuclear compound is 50% by weight or less of the part concerned, the above-mentioned properties are particularly preferable for practical purposes. The model used for the high performance liquid chromatography defined here was HLC-802UR model manufactured by Toyo Soda Co., Ltd. Next, the bonding molar ratio of phenols (P) and aldehydes (A) in the modified resol resin according to the present invention is A/
P is within the range of 1.2 to 3, especially 1.5 to 3 for practical purposes.
2.8 is preferred. The content of free phenols in the modified resol resin according to the present invention is 20.0% by weight or less in terms of nonvolatile content of the resin. This content is practically 15.0
Preferably, it is less than or equal to the weight percent. The content of free phenols here is a value measured by the bromine method. The water magnification at 25° C. of the modified resol resin of the present invention is 3.0 times the volume or more, and preferably 5.0 times the volume or more in terms of the nonvolatile content of the resin. The water magnification referred to here is a numerical value expressed as the ratio of the volume of pure water that is added to the resin by adding and mixing pure water purified by the ion exchange resin method until the resin starts to become cloudy to a certain volume of resin. be. A modified resol resin having the above-mentioned characteristic values has a large resin solid content retention during high-temperature curing, and the cured product thereof has extremely excellent flexibility. If the amount of polyhydric alcohol used in the modified resol resin of the present invention is less than 3 parts by weight per 100 parts by weight of phenol, the resin solid content retention during high temperature curing and the flexibility of the cured resin may be affected. If substantial denatured hardening is not observed, and if it exceeds 80 parts by weight, the cured resin will lose its original excellent properties such as heat resistance, abrasion resistance, and acid resistance, which is not desirable in practice. If the average molecular weight n of the modified resol resin as measured by the above-mentioned measurement method exceeds 400, the period of effective water solubility is short, resulting in poor stability. In addition, if n is less than 150, free phenols,
Since the content of low molecular weight substances such as saligenin is high, the resin solid content yield is undesirably low. Next, if the bond molar ratio A/P of phenols (P) and aldehydes (A) exceeds 3, the aldehydes will be released during curing and the volatile components will increase by that amount, so it will not be worth using the compound. is scarce. Furthermore, if the bond molar ratio A/P is less than 1.2, the curability of the resin will be extremely poor. If the amount of free phenols in the modified resol resin exceeds 20.0 percent by weight in terms of non-volatile content, the free phenols will be released as volatile components during curing, resulting in a decrease in resin solids yield and the above-mentioned adverse effects. If the water magnification of the modified resol resin at 25° C. is less than 3.0 times by volume in terms of its non-volatile content, the period of water-solubility is short, resulting in poor stability and no practical use as a water-soluble resol type phenolic resin. The polyhydric alcohol may be added to the modified resol resin of the present invention before, during, or after the reaction of the phenols and aldehydes. When the base material is caked as a binder and only the flexibility of the cured product is to be improved, it may be added and mixed after the above-mentioned reaction. Further, when the resol type phenolic resin is actually used, the resol type phenolic resin and polyhydric alcohol may be mixed in a desired amount. The modified resol resin according to the present invention has properties that allow it to be used in various applications such as caking, adhesion, and processing for organic and inorganic materials in which ordinary water-soluble resol type phenolic resins are used. EXAMPLES The present invention will be explained in detail below using Examples, but the present invention is not limited by the Examples. In addition, all "parts" and "%" described in these Examples and Comparative Examples indicate "parts by weight" and "% by weight." Example 1 1000 parts of phenol, 1380 parts of 37% formalin and 250 parts of ethylene glycol were placed in a reaction apparatus equipped with a stirrer, a reflux condenser and a thermometer, and 80 parts of a 25% aqueous sodium hydroxide solution was added and the temperature was gradually raised. I let it happen. After the temperature reached 65°C, stirring was continued at the same temperature, and heating and stirring were terminated when the water ratio at 25°C reached 15 times. After that, it was neutralized with formic acid to make the pH at 25°C 7.5, and a dehydration reaction was carried out at a reaction temperature of 50 to 60°C under reduced pressure of 30 to 40 mmHg, and the mixture was cooled to room temperature to produce modified resol resin 1950.
I got the department. Example 2 Phenol 1000 was added to the same reactor as Example 1.
2,160 parts of 37% formalin and 250 parts of propylene glycol, 50 parts of a 25% aqueous sodium hydroxide solution and 20 parts of triethylamine were added, and the temperature was gradually raised. After the temperature reached 65°C, stirring was continued at the same temperature, and heating and stirring were terminated when the water ratio at 25°C reached 15 times. Thereafter, the mixture was neutralized with formic acid to have a pH of 7.1 at 25°C to obtain 3490 parts of a modified resol resin. Comparative Example 1 1000 parts of phenol and 1380 parts of 37% formalin were charged into a reaction apparatus of the same type as in Example 1, and 80 parts of a 25% aqueous sodium hydroxide solution was added thereto, and the temperature was gradually raised. After the temperature reached 65°C, stirring was continued at the same temperature, and heating and stirring were terminated when the water ratio at 25°C reached 15 times. After neutralizing with formic acid to adjust the pH at 25°C to 7.5, a dehydration reaction was carried out at a reaction liquid temperature of 50 to 60°C under reduced pressure of 30 to 40 mmHg to obtain 1720 parts of a modified resol resin. Comparative Example 2 1000 parts of phenol and 1500 parts of 37% formalin were charged into a reactor of the same type as in Example 1, 50 parts of a 25% aqueous sodium hydroxide solution and 20 parts of triethylamine were added, and the temperature was gradually raised. After the temperature reaches 65℃, continue stirring at the same temperature until the water ratio at 25℃ is
Heating and stirring were stopped when the volume increased to 15 times. Thereafter, the mixture was neutralized with formic acid to adjust the pH at 25°C to 7.0, yielding 2585 parts of a modified resol resin. The portions from which the solvent was removed from the resins obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were subjected to high performance liquid chromatography (HLC) to determine the average molecular weight n and the content of the nuclear compound. Furthermore, free phenol, pH, water ratio, and nonvolatile content were measured.
The measurement results are shown in Table 1.

[Table] Table 2 shows the results of measuring the resin solid content retention during high temperature curing for the resol resins obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[Table] It was found that the resin solid content yields of the modified resol resins of Examples 1 and 2 were significantly superior to those of Comparative Examples 1 and 2. Next, the flexibility of the four types of resol resins was measured when they were used as a binder for paper. In other words, paper is uniformly impregnated with resol resin and heated at 200℃.
The bending resistance was measured using a Gurley type flexibility tester on test pieces that were adjusted so that the resin adhesion was 25 to 30% by weight based on the paper weight when heated and cured for 5 minutes. It is shown in Table 3.

[Table] The bending resistance of the test pieces using the modified resol resins of Examples 1 and 2 was clearly lower than that of the test pieces using the resol resins of Comparative Examples 1 and 2. It turned out that he was extremely sexually active.

Claims (1)

[Scope of Claims] 1. A method for producing a water-soluble modified resol resin, which comprises reacting phenols, aldehydes, and polyhydric alcohols in the presence of a basic catalyst. 2 The number of added polyhydric alcohols is phenols
The method for producing a modified resol resin according to claim 1, wherein the amount is 3 to 80 parts by weight per 100 parts by weight. 3. Claim 1 or 2, wherein the polyhydric alcohol has 2 to 9 alcoholic hydroxyl groups.
A method for producing a modified resol resin as described in Section 1. 4. When the portion of the modified resol resin excluding the solvent is measured by high performance liquid chromatography, the average molecular weight n is within the range of 150 to 400, and the content of phenol mononuclear compound in this portion is within the range of 150 to 400. The method for producing a modified resol resin according to claim 1, item 2 or 3, wherein the content is 60% by weight or less. 5. Modification according to claim 1, 2, 3, or 4, wherein the bond molar ratio A/P of phenols (P) and aldehydes (A) is within the range of 1.2 to 3. A method for producing resol resin. 6. The method for producing a modified resol resin according to claim 1, 2, 3, 4, or 5, wherein the content of free phenols is 20.0% by weight or less in terms of nonvolatile content of the modified resol resin. . 7. Claims 1, 2, 3, 4, 5, or 6, wherein the water magnification at 25°C is 3.0 times or more by volume in terms of nonvolatile content of the modified resol resin. Method for producing modified resol resin.