JP7459564B2 - Method for producing lignin-modified novolac phenolic resin and method for producing crosslinked resin - Google Patents

Description

The present invention relates to a method for producing a lignin-modified novolac-type phenolic resin, and a method for producing a crosslinked body from the lignin-modified novolac-type phenolic resin.

Until now, various developments have been made in methods for producing lignin-modified phenolic resins. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes a procedure of adding formaldehyde after reacting lignin with phenol.

JP 2013-199561 A

However, as a result of study by the present inventor, the molding material using the lignin-modified phenolic resin obtained by the method described in Patent Document 1 is difficult to injection mold, and even if it can be injection molded, the curability is poor. It has been found that moldability is poor and precise molding may be difficult.

After further investigation, the inventors found that by appropriately adjusting the manufacturing process of the lignin-modified phenolic resin, it is possible to obtain a lignin-modified novolac-type phenolic resin that can be precisely injected molded. Furthermore, they found that the lignin-modified novolac-type phenolic resin obtained by further reacting a reaction product obtained by reacting lignins, phenols, and aldehydes with a novolac-type phenolic resin has excellent mechanical properties when cured.

According to the invention,
A first step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing a first reaction product and the acid catalyst ;
A novolak phenolic resin is added to the first reaction mixture, and the first reaction product and the novolak phenolic resin are reacted in the presence of the acid catalyst to produce a lignin-modified novolak phenolic resin. a second step of obtaining;
A method for producing a lignin-modified novolac-type phenolic resin is provided.

Further, according to the present invention,
A first step of obtaining a lignin-modified novolak-type phenolic resin by the above method;
A second step of mixing the lignin-modified novolac-type phenolic resin with a curing agent to obtain a crosslinked resin composition;
a third step of heat-treating the crosslinkable resin composition to obtain a crosslinked body of the crosslinkable resin composition;
The present invention provides a method for producing a crosslinked body, comprising the steps of:

According to the present invention, there are provided a method for producing a lignin-modified novolac-type phenolic resin having improved moldability, and a method for producing a crosslinked product from the lignin-modified novolac-type phenolic resin.

A method for producing a lignin-modified novolak phenolic resin according to the present embodiment will be described.
The method for producing a lignin-modified novolak phenolic resin of the present embodiment includes a first step of reacting lignin, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction product. and a second step of reacting the first reaction product with a novolac-type phenolic resin to obtain a lignin-modified novolak-type phenolic resin.

According to the findings of the present inventor, the lignin-modified novolac type phenolic resin obtained by such a production method has excellent moldability while maintaining the excellent properties inherent to phenolic resin such as heat resistance and strength. The crosslinked product (cured product) obtained by crosslinking (curing) the lignin-modified novolac type phenol resin with a crosslinking agent has excellent mechanical properties.

The method for producing the lignin-modified novolac-type phenolic resin of this embodiment is described in detail below.

The method for producing a resin composition of this embodiment includes the following steps 1 and 2.
(Step 1) A first step in which lignins, phenols, and aldehydes are reacted in the presence of an acid catalyst to obtain a first reaction product.
(Step 2) A second step in which the first reaction product obtained in the first step is reacted with a novolak-type phenolic resin to obtain a lignin-modified novolak-type phenolic resin.

In this embodiment, step 1 (first step) includes a step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing a first reaction product. Here, the first reaction product is a reaction product of lignins, phenols, and aldehydes, and is a lignin-modified phenolic resin.

In this embodiment, step 2 (second step) is a step in which the lignin-modified phenol, which is the first reaction product obtained in step 1, is reacted with an unmodified novolac-type phenolic resin to obtain a lignin-modified novolac-type phenolic resin.

<Phenols>
Examples of the phenols used in step 1 of the present embodiment include phenol, phenol derivatives, and combinations thereof. As the phenol derivative, phenol having any substituent introduced into the benzene ring can be used. Examples of the substituent include a hydroxy group; a lower alkyl group such as a methyl group or an ethyl group; a halogen atom such as fluorine, chlorine, bromine, or iodine; an amino group; a nitro group; and a carboxy group. Examples of the phenols that can be used include phenol, catechol, resorcinol, hydroquinone, o-cresol, m-cresol, p-cresol, o-fluorophenol, m-fluorophenol, p-fluorophenol, o-chlorophenol, m-chlorophenol, p-chlorophenol, o-bromophenol, m-bromophenol, p-bromophenol, o-iodophenol, m-iodophenol, p-iodophenol, o-aminophenol, m-aminophenol, p-aminophenol, o-nitrophenol, m-nitrophenol, p-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, salicylic acid, p-hydroxybenzoic acid, and combinations thereof. The phenols may be used alone or in combination of two or more.

As the phenols, alkylphenols having 2 to 18 carbon atoms can also be used. The alkylphenols may have a branched alkyl chain or an unsaturated bond. Further, the substitution position of the alkyl chain on the benzene ring may be any of ortho, meta, and para substitution. Examples of alkylphenols include ethylphenol, propylphenol, isopropylphenol, butylphenol, secondary butylphenol, tertiary butylphenol, amylphenol, tertiary aminophenol, hexylphenol, heptylphenol, octylphenol, tertiary octylphenol, nonylphenol, Tertiary nonylphenol, decylphenol, undecylphenol, dodecylphenol, tridecylphenol, tetradecylphenol, pentadecylphenol, cardanol, cardol, urushiol, hexadecylphenol, methyl cardol, heptadecylphenol, laccol, thiol, octadecyl Examples include phenol. Further, as the alkylphenols, vegetable oils such as cashew nut shell liquid (cashew oil) and sumac extract can be used.

Among these, it is preferable to use one or more phenols selected from the group consisting of phenol, cresol, xylenol, alkylphenols, and bisphenols, and from the viewpoint of production costs, it is preferable to use phenol, cresol, butylphenol, and bisphenol A.

<Lignins>
The lignins used in step 1 of this embodiment include at least one selected from lignin and lignin derivatives.
Lignin, together with cellulose and hemicellulose, is a major component forming the structure of plants and is one of the most abundant aromatic compounds in nature. Examples of lignin include pulp lignins such as kraft lignin, lignosulfonic acid, soda lignin, and soda-anthraquinone lignin; organosolv lignin; explosive lignin; lignophenol; phenolized lignin, and the like. The origin of lignin is not particularly limited, and examples thereof include wood and herbaceous plants that contain lignin and form woody parts, such as coniferous trees such as cedar, pine, and cypress, broad-leaved trees such as beech, birch, oak, and zelkova, and grasses (herbaceous plants) such as rice, wheat, corn, and bamboo.

In the present embodiment, the term "lignin derivative" refers to a compound having a unit structure constituting lignin or a structure similar to a unit structure constituting lignin. The lignin derivative has a phenol derivative as a unit structure. Since this unit structure has chemically and biologically stable carbon-carbon bonds and carbon-oxygen-carbon bonds, it is resistant to chemical deterioration and biological decomposition.

Examples of lignin derivatives include guaiacylpropane (ferulic acid) represented by formula (A) in the following formula (1), syringylpropane (sinapic acid) represented by the following formula (B), and 4-hydroxyphenylpropane (coumaric acid) represented by the following formula (C). The composition of the lignin derivatives varies depending on the biomass used as the raw material. Lignin derivatives containing mainly guaiacylpropane structures are extracted from coniferous trees. Lignin derivatives containing mainly guaiacylpropane structures and syringylpropane structures are extracted from broadleaf trees. Lignin derivatives containing mainly guaiacylpropane structures, syringylpropane structures, and 4-hydroxyphenylpropane structures are extracted from herbaceous plants.

The lignin derivative is preferably one obtained by decomposing biomass. Since biomass is formed by absorbing and immobilizing carbon dioxide in the atmosphere during the photosynthesis process, biomass contributes to suppressing the increase in carbon dioxide in the atmosphere, and the industrial use of biomass can contribute to suppressing global warming. Examples of biomass include lignocellulosic biomass. Examples of lignocellulosic biomass include leaves, bark, branches, and wood of plants containing lignin, as well as processed products thereof. Examples of plants containing lignin include the above-mentioned broadleaf trees, coniferous trees, and grass plants.

Methods for decomposing biomass include chemical treatment, hydrolysis, steam explosion, supercritical water treatment, subcritical water treatment, mechanical treatment, cresol sulfate, and pulp production. From the viewpoint of environmental load, the steam explosion, subcritical water treatment, and mechanical treatment are preferred. From the viewpoint of cost, the pulp production is preferred. Also, from the viewpoint of cost, it is preferred to use by-products of biomass utilization. Lignin derivatives can be prepared by decomposing biomass in the presence of a solvent at 150 to 400°C, 1 to 40 MPa, and 8 hours or less. Lignin derivatives can also be prepared by the methods disclosed in JP 2009-084320 A and JP 2012-201828 A.

Examples of lignin derivatives include those obtained by decomposing lignocellulose, which is a combination of lignin, cellulose, and hemicellulose. Lignin derivatives may include lignin decomposition products, cellulose decomposition products, and hemicellulose decomposition products, which are mainly composed of compounds having a lignin skeleton.

It is preferable that the lignin derivative has many reactive sites where the curing agent acts by electrophilic substitution reaction with the aromatic ring. Since less steric hindrance near the reactive sites leads to better reactivity, it is preferable that at least one of the ortho and para positions of the aromatic ring containing a phenolic hydroxyl group is unsubstituted, and lignin derived from coniferous trees or herbaceous plants, which contains many guaiacyl nucleus or 4-hydroxyphenyl nucleus structures as aromatic units of lignin, is preferable. As the lignin derivative, those disclosed in JP-A-2009-084320 and JP-A-2012-201828 can be used.

In addition to the basic structure described above, the lignin derivative may have a functional group (lignin secondary derivative).

The functional groups possessed by the secondary lignin derivatives are not particularly limited, but are preferably, for example, those in which two or more of the same functional groups can react with each other or with other functional groups. Specific examples include epoxy groups, methylol groups, vinyl groups having carbon-carbon unsaturated bonds, ethynyl groups, maleimide groups, cyanate groups, isocyanate groups, and the like. Of these, lignin derivatives into which methylol groups have been introduced (methylolized) are preferably used. Such secondary lignin derivatives undergo self-crosslinking due to a self-condensation reaction between methylol groups, and also crosslink with alkoxymethyl groups and hydroxyl groups in the crosslinking agent described below. As a result, a lignin-modified novolac-type phenolic resin having a particularly homogeneous and rigid skeleton and excellent solvent resistance is obtained.

Furthermore, the lignin derivative in the present disclosure may have a carboxyl group. Lignin-modified novolak phenolic resin obtained from a lignin derivative having a carboxyl group has many crosslinking points for the crosslinking agent described below, so the crosslinking density of the resulting crosslinked product can be improved, resulting in improved solvent resistance. A crosslinked product with excellent properties can be obtained.

In addition, if the above-mentioned lignin derivative has a carboxyl group, the carboxyl group can be confirmed by the presence or absence of absorption of a peak at 172 to 174 ppm when subjected to ¹³ C-NMR analysis attributed to the carboxyl group. can.

<Aldehydes>
Examples of the aldehydes used in step 1 of the present embodiment include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butylaldehyde, caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, and paraxylene dimethyl ether. Preferred examples include formaldehyde, paraformaldehyde, trioxane, polyoxymethylene, acetaldehyde, paraxylene dimethyl ether, and combinations thereof. The aldehydes may be used alone or in combination of two or more. Among these, from the viewpoints of productivity and cost, it is preferable to use formaldehyde or acetaldehyde.

<Acid catalyst>
The acid catalyst used in step 1 of this embodiment may be any acid that can be used as a reaction catalyst, and may be an organic acid, an inorganic acid, or a combination thereof. Examples of organic acids include acetic acid, formic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, benzoic acid, salicylic acid, sulfonic acid, phenolsulfonic acid, and paratoluenesulfonic acid. Examples of inorganic acids include hydrochloric acid, sulfuric acid, sulfates, phosphoric acid, and phosphates.

In the above step 1, the molar ratio of aldehydes (F) to phenols (P) (F/P molar ratio) is, for example, 0.45 to 1.0, and preferably 0.6 to 0.9. By using aldehydes in the above range, the amount of unreacted remaining phenols can be reduced.

The reaction temperature in step 1 above may be, for example, 60°C to 120°C, preferably 80°C to 100°C. This allows the reaction to proceed efficiently and sufficiently. The reaction time is not particularly limited and may be appropriately determined depending on the type of starting materials, molar ratio of the mixture, amount and type of catalyst used, and reaction conditions.

The raw materials used in step 1 above may contain components other than phenols and aldehydes, and the raw material components may be added all at once or in multiple portions.

Although it is preferable to carry out step 1 without a solvent, an organic solvent or water may be used as the solvent. Examples of the organic solvent include alcohols, ketones, esters, ethers, and hydrocarbons. Examples of alcohols include methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, octanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin, and the like. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone. Examples of the esters include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methoxybutyl acetate, amyl acetate, methyl lactate, ethyl lactate, butyl lactate, and the like. Ethers include propyl ether, dioxane, methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl carbitol, ethyl carbitol. , butyl carbitol, methyl cellosolve acetate, ethyl cellosolve acetate, propyl cellosolve acetate, butyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate. Examples of hydrocarbons include toluene, xylene, pentane, hexane, cyclohexane, heptane, octane, decane, solvent naphtha, industrial gasoline, petroleum ether, petroleum benzine, ligroin, and the like. These may be used alone or in combination of two or more.

After step 1 and before step 2, a dehydration step may be performed to dehydrate the first reaction mixture containing the first reaction product obtained in step 1. As a dehydration method, reduced pressure dehydration may be used, but normal pressure dehydration may also be used. For example, the degree of vacuum during reduced pressure dehydration may be, for example, 110 torr or less, and more preferably 80 torr or less.

After step 1 and before step 2, a removal step may be carried out to remove unreacted phenols remaining in the reaction solution obtained in step 1. As the removal step, a process for removing unreacted phenols by a normal demonomerization process can be used.

After step 1, step 2 is carried out. Step 2 includes mixing a novolac phenolic resin with the first reaction product obtained in step 1. The novolac phenolic resin may be added to the reaction mixture containing the first reaction product obtained in step 1 all at once, or may be added in multiple portions.

In step 2, the step of mixing the novolac-type phenolic resin is preferably carried out under heating. If the lignin-modified phenolic resin, which is the first reaction product obtained in step 1, and the novolac-type phenolic resin are simply mixed in the solid state without being heated and melted, the crosslinking reaction with the crosslinking agent of the obtained lignin-modified novolac-type phenolic resin may not proceed uniformly, and the mechanical strength of the obtained crosslinked body may decrease. In contrast, according to the preferred embodiment, by reacting the unmodified novolac-type phenolic resin with the heated lignin-modified phenolic resin obtained in step 1, these are mixed uniformly, and the obtained lignin-modified novolac-type phenolic resin can be uniformly cured due to intermolecular entanglement and intermolecular action, thereby realizing molding with excellent dimensional accuracy.

Here, when the molecular weight of the lignin-modified novolac-type phenolic resin is increased by adjusting the reaction ratio of the phenols, lignins, and aldehydes, the viscosity of the reaction product increases and dehydration becomes difficult, which may result in a longer process time and a larger amount of unreacted phenols remaining.
In contrast, in the present embodiment, the process time can be shortened and the resin yield can be increased compared to the case where the molecular weight is increased by the reaction ratio of the above-mentioned phenols, lignins, and aldehydes. In addition, by adjusting the molecular weight, molecular weight distribution, and addition amount of the unmodified novolac-type phenolic resin, the characteristics of the obtained lignin-modified phenolic resin and the physical properties of the resin material can be easily adjusted according to the purpose.

In this embodiment, the structure may not include a step of lowering the reaction mixture obtained in step 1 to room temperature 25° C. between step 1 and step 2. That is, in the manufacturing method of this embodiment, it is preferable to perform Step 1 and Step 2 under heating.

By carrying out steps 1 and 2 under heating, it is possible to obtain a lignin-modified novolac-type phenolic resin for molding materials that is not only superior in productivity but also has excellent mechanical properties and dimensional accuracy compared to the case of melt-mixing a solid novolac-type phenolic resin and a lignin-modified phenolic resin. Although the detailed mechanism is unknown, the lignin-modified novolac-type phenolic resin obtained by the manufacturing method of this embodiment has improved dispersibility of the lignin-modified phenolic resin in the unmodified novolac-type phenolic resin, and the hardening reaction becomes uniform due to the intermolecular entanglement and intermolecular reaction between the novolac-type phenolic resin and the lignin-modified phenolic resin, making it possible to mold with excellent dimensional accuracy, and furthermore, the obtained molded body has excellent mechanical strength.

Further, in step 2, an unmodified novolac type phenol resin may be added to the first reaction mixture obtained in step 1. That is, the reaction mixture containing the unreacted raw materials, the remaining acid catalyst, and the generated lignin-modified phenol resin (first reaction product) obtained in step 1 is subjected to neutralization treatment of the acid catalyst, The unmodified novolac type phenolic resin may be added without any post-treatment such as isolation or extraction of the lignin-modified phenolic resin.

<Novolac type phenolic resin>
A specific example of the novolak phenolic resin used in the present disclosure (herein sometimes referred to as "unmodified novolak phenolic resin") is one in which phenols and aldehydes are reacted without a catalyst or in the presence of a catalyst. Examples include phenol resins, cresol resins, xylenol resins, naphthol resins, etc., which can be obtained in a random novolac type or a high ortho-novolak type. Also, bisphenol F (4,4-methylenebisphenol, 2,4-methylenebisphenol, 2,2-methylenebisphenol), bisphenol A (2,2-bis(4-hydroxyphenyl)propane), bisphenol S (2,2- bis(4-hydroxyphenyl) sulfone), bisphenol E (4,4-ethylidene bisphenol), bisphenol fluorene (4,4-(9H-fluoren-9-ylidene) bisphenol), 4,4-methylidene bis(2,6- Bisphenols such as dimethylphenol) and bis(4-hydroxyphenyl)methanone can also be used as they are.

The weight average molecular weight (Mw) of the unmodified Novoc type phenolic resin used in this embodiment is 10,000 or more and 30,000 or less, more preferably 12,000 or more and 20,000 or less. Below the lower limit, the effect of improving the curability of the resulting lignin-modified novolak phenolic resin and the physical properties of the cured product is low, and above the upper limit, in the step of adding unmodified novolak phenolic resin in step 2, The melt viscosity of the resulting mixture increases, and the productivity of the desired phenolic resin decreases. Furthermore, the increased viscosity of the obtained lignin-modified novolak phenolic resin reduces the fluidity of the resin during molding, leading to a decrease in moldability and processability.

In step 2, the amount of unmodified novolac phenolic resin added is 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less, based on the total amount of phenols and lignins. Below the lower limit, the effect of improving the curability of the obtained lignin-modified novolac phenolic resin and the physical properties of the cured product is low, and above the upper limit, the melt viscosity of the obtained mixture increases in the addition process of the unmodified novolac phenolic resin in step 2, and the viscosity of the obtained lignin-modified novolac phenolic resin increases, which may reduce the fluidity of the resin during molding and lead to reduced moldability and processability.

In the manufacturing method of this embodiment, steps 1 and 2 may be performed consecutively, or other steps may be included between steps 1 and 2.

A lignin-modified novolac-type phenolic resin can be isolated from the reaction mixture obtained in the above steps. In the above reaction steps, by selecting an appropriate F/P value under acidic conditions, the lignin-modified novolac-type phenolic resin can have both a structure derived from the lignin-modified phenolic resin obtained in step 1 and a structure derived from the novolac-type phenolic resin used in step 2.

The lignin-modified novolac type phenolic resin obtained through the above steps 1 and 2 has a weight average molecular weight of, for example, 4,000 to 30,000, preferably 5,000 to 25,000. The weight average molecular weight of the lignin-modified novolak phenolic resin can be adjusted by appropriately changing the reaction conditions.

The lignin modification rate of the lignin-modified phenol resin is 10% or more and 40% or less, preferably 12% or more and 35% or less, more preferably 15% or more and 30% or less.

The lignin-modified novolac-type phenolic resin obtained as described above is suitable for use, for example, as a resin material for injection molding. The lignin-modified novolac-type phenolic resin obtained by the method of this embodiment can be precisely injection molded, and molded products with excellent dimensional accuracy can be obtained, and the molded products have excellent mechanical properties such as strength and elastic modulus.

The lignin-modified novolac-type phenolic resin obtained by the method of this embodiment can be subjected to a crosslinking reaction with a crosslinker to form a crosslinked body. The crosslinked body can be used as a molded body for any purpose.

The method for producing the crosslinked body of this embodiment includes a first step of obtaining a lignin-modified novolac-type phenolic resin by the above-mentioned method, a second step of mixing the lignin-modified novolac-type phenolic resin with a curing agent to obtain a crosslinked resin composition, and a third step of heat-treating the crosslinked resin composition to obtain a crosslinked body of the crosslinked resin composition.

As the curing agent, for example, an amine curing agent can be used. As the amine curing agent, specifically, hexamethylenetetramine, hexamethoxymethylolmelamine, etc. can be used. As the amine curing agent, it is preferable to use, for example, hexamethylenetetramine.

The content of the curing agent is, for example, 7 parts by weight to 30 parts by weight, and preferably 10 parts by weight to 25 parts by weight, based on 100 parts by weight of the lignin-modified novolac type phenolic resin. By setting it within the above numerical range, a crosslinked resin composition having good curability can be obtained. In this specification, "~" indicates that the upper limit value and the lower limit value are included, unless otherwise specified.

The second step in the method for producing the crosslinked body of this embodiment can include a step of further mixing a filler. That is, the crosslinked resin composition can include a lignin-modified novolac-type phenolic resin, a curing agent, and a filler.

As the above-mentioned filler, for example, a fibrous base material, an organic filler, an inorganic filler, etc. can be used. The fibrous base material is a filler having a fibrous form. The organic filler and the inorganic filler may each be either a granular filler or a plate-like filler. The plate-like filler is a filler having a plate shape. The granular filler is a filler having a shape other than a fibrous or plate shape, including an irregular shape. These may be used alone or in combination of two or more kinds.

As the granular filler, for example, granular inorganic fillers can be used, such as glass beads, glass powder, calcium carbonate, talc, silica, aluminum hydroxide, clay, and mica.

Examples of the fibrous filler include glass fiber, carbon fiber, asbestos fiber, metal fiber, wollastonite, attapulgite, sepiolite, rock wool, aluminum borate whisker, potassium titanate fiber, calcium carbonate whisker, and titanium oxide whisker. , fibrous inorganic fillers such as ceramic fibers; fibrous organic fillers such as aramid fibers, polyimide fibers, and poly(paraphenylenebenzobisoxazole fibers).These may be used alone or in combination of two types. The above may be used in combination.

Examples of the plate-like filler and granular filler include talc, kaolin clay, calcium carbonate, zinc oxide, calcium silicate hydrate, mica, glass flakes, glass powder, magnesium carbonate, silica, titanium oxide, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium sulfate, calcium sulfite, zinc borate, barium metaborate, aluminum borate, calcium borate, sodium borate, aluminum nitride, boron nitride, silicon nitride, and pulverized products of the above fibrous fillers.

The content of the filler in the crosslinked resin composition is, for example, 120 to 500 parts by mass, preferably 130 to 400 parts by mass, and more preferably 150 to 300 parts by mass, relative to 100 parts by mass of the lignin-modified novolac-type phenolic resin. By making the content equal to or greater than the lower limit, the resin composition containing the lignin-modified novolac-type phenolic resin can be molded with excellent dimensional accuracy. In addition, the mechanical strength of the resulting cured product can be increased. By making the content equal to or less than the upper limit, the manufacturing stability of the crosslinked body (molded body) can be increased.

The crosslinked resin composition for producing the crosslinked body of this embodiment may contain other components in addition to the above-mentioned components, as long as the purpose of the present invention is not impaired. Examples of such other components include additives such as elastomers, curing accelerators, resin components, release agents, pigments, flame retardants, adhesion improvers, and coupling agents. The crosslinked resin composition may contain a solvent.

Examples of the elastomer include, but are not particularly limited to, acrylonitrile butadiene rubber, isoprene, styrene butadiene rubber, ethylene propylene rubber, and the like. Among these, acrylonitrile butadiene rubber is preferred. Particularly, toughness can be imparted by using an elastomer.

The above-mentioned curing accelerator is not particularly limited, and a conventional curing accelerator can be used, for example, an oxide or hydroxide of an alkaline earth metal such as magnesium oxide, calcium hydroxide, or barium hydroxide, or an aromatic carboxylic acid such as salicylic acid or benzoic acid. The above-mentioned curing accelerator is used in an amount of, for example, 0.5 to 20 parts by mass per 100 parts by mass of the lignin-modified novolac-type phenolic resin.

The above resin components include urea resin, resins having a triazine ring such as melamine resin, bismaleimide resin, polyurethane resin, silicone resin, resins having a benzoxazine ring, cyanate ester resin, polyvinyl butyral resin, and polyvinyl acetate resin. If necessary, a combination of these resins can be used.

Examples of the mold release agent include stearic acid, calcium stearate, zinc stearate, and polyethylene.

Examples of the pigment include carbon black.

The crosslinked resin composition is produced by melt-kneading the lignin-modified novolak phenolic resin, the curing agent, and the filler, if used, in a kneader, roll, etc., and then uniformly mixing it with the other components mentioned above, or by blending. It is obtained by melt-kneading all raw material components using a kneading device such as a roll, a co-kneader, or a twin-screw extruder alone or in combination with a roll and other mixing device, and then granulating or pulverizing the mixture. In this embodiment, the crosslinked resin composition is
For example, it is provided in the form of powder, granules, tablets, sheets, or the like.

The resulting cross-linked resin composition can be molded by heat treatment to obtain a molded product (cross-linked body) made of the cured resin composition.

The molding method for the molded product is not particularly limited, but for example, transfer molding, compression molding, injection molding, etc. can be used.

Examples of molded articles of this embodiment include molded articles used in automobiles, aircraft, railway vehicles, ships, general-purpose machines, household electrical appliances, and peripheral parts thereof, as well as molded articles used in the housings, structural/mechanical parts, and electrical/electronic parts thereof.

Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.
Examples of embodiments are given below.
1. A first step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction product;
A second step of reacting the first reaction product with a novolac phenolic resin to obtain a lignin-modified novolac phenolic resin.
A method for producing a lignin-modified novolac-type phenolic resin.
2. The method for producing a lignin-modified novolac-type phenolic resin according to 1., wherein in the first step, a molar ratio of the aldehydes to the phenols (F/P) is 0.45 or more and 1.0 or less.
3. The method for producing a lignin-modified novolac-type phenolic resin according to 1. or 2., wherein the weight average molecular weight of the lignin-modified novolac-type phenolic resin is 4,000 or more and 30,000 or less.
4. The method for producing a lignin-modified novolac-type phenolic resin according to any one of 1. to 3., wherein the weight average molecular weight of the novolac-type phenolic resin is 10,000 or more and 30,000 or less.
5. The method for producing a lignin-modified novolac-type phenolic resin according to any one of 1. to 4., wherein in the second step, the amount of the novolac-type phenolic resin is 10% by mass or more and 50% by mass or less based on the total amount of the phenols and the lignins.
6. The method for producing a lignin-modified novolak-type phenolic resin according to any one of 1. to 5., wherein the first step and the second step are carried out under heating.
7. The method for producing a lignin-modified novolac-type phenolic resin according to any one of 1. to 6., wherein the first step comprises a step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing the first reaction product, and a step of removing water from the first reaction mixture.
8. The method for producing a lignin-modified novolac-type phenolic resin according to any one of 1. to 7., wherein the first step comprises a step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing the first reaction product, and a step of removing unreacted phenols from the first reaction mixture.
9. The first step includes a step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing the first reaction product;
9. The method for producing a lignin-modified novolac-type phenolic resin according to any one of 1. to 8., wherein the second step includes a step of adding the novolac-type phenolic resin to the first reaction mixture.
10. The method for producing a lignin-modified novolac-type phenolic resin according to any one of 1. to 9., wherein the lignins include lignin or a lignin derivative.
11. The method for producing a lignin-modified novolak-type phenolic resin according to any one of 1. to 10., wherein the aldehydes include formaldehyde or acetaldehyde.
12. The method for producing a lignin-modified novolak-type phenolic resin according to any one of 1. to 11., wherein the phenols include at least one selected from the group consisting of phenol, cresol, xylenol, alkylphenols and bisphenols.
13. The method for producing a lignin-modified novolac-type phenolic resin according to any one of 1. to 12., wherein the lignin modification rate of the phenol-modified novolac-type phenolic resin is 10% or more and 40% or less.
14. A first step of obtaining a lignin-modified novolak-type phenolic resin by any one of the methods described in 1. to 13.;
A second step of mixing the lignin-modified novolac-type phenolic resin with a curing agent to obtain a crosslinked resin composition;
a third step of heat-treating the crosslinkable resin composition to obtain a crosslinked body of the crosslinkable resin composition;
A method for producing a crosslinked body, comprising:
15. The method for producing a crosslinked body according to 14., wherein the curing agent contains hexamethylenetetramine.
16. The method for producing a crosslinked body according to 14. or 15., wherein the second step further comprises a step of mixing a filler.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the description of these Examples.

<Preparation of resin material>
(Synthesis of resin material A1)
A three-neck flask equipped with a stirrer and a thermometer was charged with 900 parts by mass of phenol, 307 parts by mass of lignin, and 12 parts by mass of oxalic acid, and heated to 100 ° C., and 450 parts by mass of 37% formalin was dropped over 30 minutes, and after the dropwise addition, the mixture was stirred at 100 ° C. for 1 hour. Next, the condensation water and unreacted phenol were distilled off by vacuum distillation while raising the temperature, and when the residual phenol became 2% or less, 490 parts by mass of novolac-type phenolic resin with a number average molecular weight (Mn) of 1,520 and a weight average molecular weight (Mw) of 14,500 was added to the flask and mixed. After stirring for 30 minutes in a molten state, the product was removed from the flask, and 1,535 parts by mass of lignin-modified novolac-type phenolic resin (resin material A1) with a lignin modification rate of 20% was obtained. The yield was 82%. The amount of novolac-type phenolic resin used was 41% by mass with respect to the total amount of phenol and lignin.

(Synthesis of resin material A2)
A three-neck flask equipped with a stirrer and a thermometer was charged with 900 parts by mass of phenol, 376 parts by mass of lignin, and 13 parts by mass of oxalic acid, and heated to 100 ° C., and 457 parts by mass of 37% formalin was dropped over 30 minutes, and after the dropwise addition, the mixture was stirred at 100 ° C. for 1 hour. Next, the condensation water and unreacted phenol were distilled off by vacuum distillation while raising the temperature, and when the residual phenol became 2% or less, 381 parts by mass of a phenol novolac resin having a number average molecular weight (Mn) of 1,280 and a weight average molecular weight (Mw) of 12,400 was added to the flask and mixed. After stirring for 30 minutes in a molten state, the product was removed from the flask, and 1,505 parts by mass of a lignin-modified novolac-type phenolic resin (resin material A2) with a lignin modification rate of 25% was obtained. The resin yield was 82%. The amount of the novolac-type phenolic resin used was 30% by mass with respect to the total amount of phenol and lignin.

(Synthesis of resin material A3)
A three-neck flask equipped with a stirrer and a thermometer was charged with 900 parts by mass of phenol, 455 parts by mass of lignin, and 14 parts by mass of oxalic acid, and heated to 100 ° C., and 456 parts by mass of 37% formalin was dropped over 30 minutes, and after the dropwise addition, the mixture was stirred at 100 ° C. for 1 hour. Next, the condensation water and unreacted phenol were distilled off by vacuum distillation while raising the temperature, and when the residual phenol became 2% or less, 356 parts by mass of a phenol novolac resin having a number average molecular weight (Mn) of 1,250 and a weight average molecular weight (Mw) of 8,800 was added to the flask and mixed. After stirring for 30 minutes in a molten state, the product was removed from the flask, and 1,520 parts by mass of a lignin-modified novolac-type phenolic resin (resin material A3) with a lignin modification rate of 30% was obtained. The resin yield was 81%. The amount of the novolac-type phenolic resin used was 26% by mass with respect to the total amount of phenol and lignin.

(Resin material B)
As resin material B, a novolac type phenol resin (manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-53195) was used.

(Preparation of resin material C1)
A three-neck flask equipped with a stirrer and a thermometer was charged with 300 parts by mass (20% by mass) of lignin and 1,200 parts by mass (80% by mass) of a phenolic resin (manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-53195), which were stirred and mixed under heating to melt. The mixture was then removed from the flask in a molten state to obtain a mixture of lignin and phenolic resin (resin material C1).

(Preparation of resin material C2)
450 parts by mass (30 mass%) of lignin and 1,050 parts by mass (70 mass%) of phenol resin (manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-53195) were placed in a three-necked flask equipped with a stirrer and a thermometer. After charging and stirring and mixing under heating and melting, the mixture was taken out of the flask in a molten state to obtain a mixture of lignin and phenol resin (resin material C2).

(Synthesis of resin material D1)
After adding 1,380 parts by mass of phenol and 17 parts by mass of oxalic acid to a three-necked flask equipped with a stirrer and a thermometer, 300 parts by mass of lignin was charged and heated to 100°C, 810 parts by mass of 37% formalin was dropped over 30 minutes, and after the dropwise addition, the mixture was stirred at 100°C for 1 hour. Next, the condensed water and unreacted phenol were distilled off by reduced pressure distillation while increasing the temperature, and when the residual phenol was 2% or less, the product was taken out of the flask, and 1,510 parts by mass of a lignin-modified novolac-type phenolic resin (resin material D1) with a lignin modification rate of 20% was obtained. The resin yield was 76%.

(Synthesis of resin material D2)
After adding 1,200 parts by mass of phenol and 17 parts by mass of oxalic acid to a three-necked flask equipped with a stirrer and a thermometer, 450 parts by mass of lignin was charged and heated to 100°C, 700 parts by mass of 37% formalin was dropped over 30 minutes, and after the dropwise addition, the mixture was stirred at 100°C for 1 hour. Next, while raising the temperature, condensation water and unreacted phenol were distilled off by reduced pressure distillation, and when the residual phenol was 2% or less, the product was taken out of the flask, and 1,502 parts by mass of a lignin-modified novolac-type phenolic resin (resin material D2) with a lignin modification rate of 30% was obtained. The resin yield was 79%.

Molded bodies were produced using the obtained resin materials A1 to D2, and the obtained molded bodies were evaluated on the following items.

<Preparation of Molded Product>
To 100 parts by mass of the resin material (resin materials A1 to D2 obtained), 15 parts by mass of hexamethylenetetramine (curing agent) was added at room temperature, and the mixture was ground and mixed to prepare a resin composition.
The obtained crosslinked resin composition was mixed with 160 parts by weight of glass fiber (filler, glass milled fiber, manufactured by Nitto Boseki Co., Ltd., standard fiber diameter 10±1.5 μm, average fiber length 90 μm) and 8 parts by weight of additives (stearic acid (manufactured by Nippon Oil & Fats Co., Ltd.), carbon black (manufactured by Mitsubishi Chemical Corporation, #5)), and the mixture was kneaded with a heated roll at about 90° C. for about 5 minutes, cooled, and then pulverized to obtain a molding material.
The obtained molding material was transfer molded under conditions of 175°C, 20 MPa, and 3 min, and further heat-treated at 180°C for 8 h to obtain a molded product (cured product of the resin material). The obtained molded product was evaluated for the following items. The results are shown in Table 1.

・Mechanical properties (flexural properties at room temperature)
In accordance with JIS K 6911 "General Test Method for Thermosetting Plastics," the flexural modulus and flexural strength were measured at 25° C. Specifically, a three-point bending test was performed using a precision universal testing machine (Autograph AG-Xplus, manufactured by Shimadzu Corporation) with a load applied at a speed of 2 mm/min.
・Mechanical properties (heat bending properties)
At 150° C., the flexural modulus and flexural strength were measured in the same manner as above.
・Mechanical properties (impact strength)
The Charpy impact strength was measured in accordance with JIS K 6911 "General testing method for thermosetting plastics."
・Electrical properties (insulation resistance)
The insulation resistance was measured in accordance with JIS K 6911 "General testing method for thermosetting plastics."
・Dimensional accuracy characteristics (molding shrinkage rate)
The molding shrinkage immediately after molding was measured in accordance with JIS K 6911 "General testing method for thermosetting plastics."

The resin materials of Examples 1 to 3 exhibited the same or higher mechanical properties (flexural strength, flexural modulus, Charpy impact strength) and electrical properties (insulation resistance value) compared to Comparative Examples 1 to 5, The results showed that the molded product had excellent dimensional accuracy characteristics.

Claims (15)

A first step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing a first reaction product and the acid catalyst ;
A novolak phenolic resin is added to the first reaction mixture, and the first reaction product and the novolak phenolic resin are reacted in the presence of the acid catalyst to produce a lignin-modified novolak phenolic resin. a second step of obtaining;
A method for producing a lignin-modified novolac type phenolic resin. The method for producing a lignin-modified novolak phenolic resin according to claim 1, wherein in the first step, the molar ratio (F/P) of the aldehyde to the phenol is 0.45 or more and 1.0 or less. . The method for producing a lignin-modified novolac-type phenolic resin according to claim 1 or 2, wherein the weight average molecular weight of the lignin-modified novolac-type phenolic resin is 4,000 or more and 30,000 or less. The method for producing a lignin-modified novolac-type phenolic resin according to any one of claims 1 to 3, wherein the weight average molecular weight of the novolac-type phenolic resin is 10,000 or more and 30,000 or less. Any one of claims 1 to 4, wherein in the second step, the novolac type phenolic resin is used in an amount of 10% by mass or more and 50% by mass or less based on the total amount of the phenols and the lignins. A method for producing a lignin-modified novolac type phenolic resin as described above. The method for producing a lignin-modified novolak phenolic resin according to any one of claims 1 to 5, wherein the first step and the second step are performed under heating. The method for producing a lignin-modified novolac-type phenolic resin according to any one of claims 1 to 6, wherein the first step comprises: reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing the first reaction product and the acid catalyst ; and removing water from the first reaction mixture. The method for producing a lignin-modified novolac-type phenolic resin according to any one of claims 1 to 7, wherein the first step comprises: reacting lignins, phenols, and aldehydes in the presence of an acid catalyst to obtain a first reaction mixture containing the first reaction product and the acid catalyst ; and removing unreacted phenols from the first reaction mixture. The method for producing a lignin-modified novolac-type phenolic resin according to any one of claims 1 to 8 , wherein the lignins include lignin or a lignin derivative. The method for producing a lignin-modified novolak-type phenolic resin according to any one of claims 1 to 9 , wherein the aldehydes include formaldehyde or acetaldehyde. The method for producing a lignin-modified novolak phenolic resin according to any one of claims 1 to 10 , wherein the phenols include one or more selected from the group consisting of phenol, cresol, xylenol, alkylphenol, and bisphenol. The method for producing a lignin -modified novolac-type phenolic resin according to any one of claims 1 to 11 , wherein the lignin-modified novolac-type phenolic resin has a lignin modification rate of 10% or more and 40% or less. A first step of obtaining a lignin-modified novolac type phenolic resin by the method according to any one of claims 1 to 12 ;
a second step of mixing a curing agent with the lignin-modified novolac-type phenolic resin to obtain a cross-linked resin composition;
a third step of heating the crosslinked resin composition to obtain a crosslinked product of the crosslinked resin composition;
A method for producing a crosslinked product, including: The method for producing a crosslinked body according to claim 13 , wherein the curing agent comprises hexamethylenetetramine. The method for producing a crosslinked body according to claim 13 or 14 , wherein the second step further includes a step of mixing a filler.