JP5671430B2 - Modified lignin and phenolic resin molding material containing the same - Google Patents

Description

  The present invention relates to a modified lignin and a phenol resin molding material containing the same.

  In recent years, effective use of plant-derived raw materials for plastic materials is expected from the viewpoint of environmental conservation. Plant-derived components mainly include cellulose, hemicellulose, lignin and the like. Of these, lignin is not easily decomposed by microorganisms, is insoluble in solvents, and is infusible, so that it is difficult to handle, and it has poor reactivity with various plastic materials. Therefore, lignin has not found a useful use so far in terms of effective use for plastic materials. For example, as described in Patent Document 1, even when natural lignin is mixed with a phenol resin, which is one of thermosetting plastics, as it is, the molding material has poor moldability and is difficult to mold. .

  Thus, Patent Document 1 describes a method for producing a lignin-modified novolak-type phenol resin obtained by reacting lignin, phenol or a derivative thereof, and aldehydes in the presence of an organic acid.

  In Patent Document 1, lignin is acid-decomposed to have a low molecular weight so as to have reactivity, and is combined with a phenol resin. However, lowering the molecular weight of lignin requires complicated operations such as neutralization in the case of acid decomposition and appropriate equipment, and generally requires enormous energy (cost) and large-scale equipment. In addition, a resin molding material or a molded product using lignin having a low molecular weight cannot be practically used.

JP 2008-156601 A

  An object of the present invention is to obtain a simple manufacturing method in which a raw material is heated for a short time without using a solvent, and to reduce the moldability of a molding material when used as a component of a phenol resin molding material. And to provide a modified lignin having reactivity to improve the mechanical strength and water resistance of the molded product.

As a result of intensive studies to solve the above problems, the present inventors have found a solution means having the following configuration, and have completed the present invention.
(1) Modified lignin having a benzoxazine ring in the molecule.
(2) The modified lignin according to (1), wherein the oxazine ring part of the benzoxazine ring is an oxazine ring derived from amines and aldehydes.
(3) The modified lignin according to (1) or (2), wherein the lignin before modification is derived from a herbaceous plant.
(4) The modified lignin according to any one of (1) to (3), wherein the lignin before modification contains an H-type basic skeleton in a proportion of 5% by mass or more.
(5) The modified lignin according to any one of (2) to (4), wherein the amine is aniline.
(6) The modified lignin according to any one of (2) to (5), wherein the aldehyde is paraformaldehyde.
(7) A phenol resin molding material containing the phenol resin and the modified lignin according to any one of (1) to (6).
(8) The phenol resin molding material according to (7), which contains 10 to 300 parts by mass of modified lignin with respect to 100 parts by mass of the phenol resin.
(9) A molded product obtained by molding the modified lignin-containing phenol resin molding material according to (7) or (8).
(10) A method for producing a modified lignin having a benzoxazine ring in the molecule, comprising a step of reacting lignin, an amine and an aldehyde.
(11) The production method according to (10), wherein 3 to 10 mol of amines and 6 to 20 mol of aldehydes are used with respect to 1 mol of lignin.
(12) The production method according to (10) or (11), wherein the lignin is lignin in a dry powder form.

  According to the present invention, a modified lignin having reactivity in an intact state can be obtained by a simple production method without reducing the molecular weight of lignin, and the phenol resin molding material containing the modified lignin is obtained by molding a molding material. The effect of improving the mechanical strength and water resistance of the molded product can be obtained without reducing the properties. Moreover, since the phenol resin molding material of this invention is a thermosetting resin containing the biomass which aimed at the effective utilization of the lignin which was almost discarded until now, it is useful also for environmental conservation. Furthermore, since the lignin can be used as it is without reducing its molecular weight, the lignin can be used at low cost.

  The modified lignin of the present invention has a benzoxazine ring in the molecule. The lignin used as the raw material of the modified lignin of the present invention (that is, the lignin before modification) is not particularly limited as long as it can be modified. The benzoxazine ring is represented by the following formula (I).

  Lignin is contained in a waste liquid called “black liquor” that is discharged when paper is produced from pulp, for example, pulp production by a soda method. The basic skeleton of lignin mainly includes G type, S type and H type. In addition, the arrow (->) in a formula shows a highly reactive carbon atom.

  Generally, lignin obtained from coniferous pulp waste liquor has G-type basic skeleton, and lignin obtained from hardwood pulp waste liquor has G-type and S-type basic skeleton. That is, lignin derived from woody plants does not contain lignin having H-type basic skeleton.

  On the other hand, herbaceous plant-derived lignin includes all of H-type, G-type and S-type, and differs in basic skeleton from wood-based plant-derived lignin in that it contains H-type.

Form G has one methoxy group (-OCH ₃₎ in the ortho position of the phenol skeleton parts, whereas S-type has two methoxy groups at the ortho position, the H-type, in the ortho position It does not have a methoxy group. The modification of the phenolic hydroxyl group by the benzoxazine ring requires that the ortho position of the phenol skeleton is vacant. Therefore, lignin derived from herbaceous plants containing H-type has less modification of the ortho position of the aromatic nucleus than lignin derived from woody plants not containing H-type, so that a highly reactive modified lignin is produced. Can do.

  Therefore, the lignin used in the present invention is preferably a lignin derived from a herbaceous plant, more preferably a lignin derived from wheat straw, rice straw or the like. The lignin used in the present invention preferably contains an H-type basic skeleton in a proportion of 5% by mass or more, more preferably 10% by mass or more. As the proportion of H-type increases, a benzoxazine-modified lignin having high reactivity as described above is easily obtained (the phenol skeleton portion is easily modified (cyclized)). The lignin used in the present invention is not limited to the lignin derived from the herbaceous plant, and the lignin derived from the herbaceous plant and the lignin derived from the woody plant may be mixed and used. Although the properties are slightly inferior, only lignin derived from woody plants may be used.

  The lignin used as a raw material is used in the form of a dry powder, for example. The drying method is not particularly limited, and may be performed before or after powdering. For example, what is necessary is just to dry for about 20 minutes-2 hours at 100-200 degreeC using a drying furnace.

  Lignin powdering is not limited to normal mills such as ball mills, hammer mills, roll mills, but also jet mills (eg swirling jet mills, opposed jet mills, wall impingement jet mills), ong mills, mortars, multistages You may perform using a mortar type kneading extruder. The powdered lignin preferably has an average particle size of 0.1 to 1000 μm, more preferably 0.1 to 500 μm.

  Since the modified lignin of the present invention has a benzoxazine ring in the lignin molecule, the reactivity with various resins is improved. That is, since the reactivity of the phenolic hydroxyl group (—OH) in the lignin molecule is poor, the modified lignin of the present invention improves the reactivity by modifying this hydroxyl group into a benzoxazine ring. Therefore, when lignin is used, complicated work such as acid decomposition to lower the molecular weight becomes unnecessary. The benzoxazine ring is preferably present on the surface of the lignin particle.

  The benzoxazine ring is formed on the phenol backbone in the lignin molecule. For example, by mixing and reacting lignin, amines, and aldehydes, a cyclization reaction proceeds at the phenol skeleton, and a benzoxazine ring represented by the above formula (I) is formed.

  Examples of amines used include primary amines, and alkyl monoamines such as methylamine, ethylamine, n-propylamine, n-butylamine, n-dodecylamine, n-nonylamine, cyclopentylamine, cyclohexylamine, and allylamine. And alkenyl monoamines, aniline, p-cyanoaniline, p-bromoaniline, o-toluidine, m-toluidine, p-toluidine, 2,4-xylidine, 2,5-xylidine, 3,4-xylidine, α- And aromatic monoamines such as naphthylamine, β-naphthylamine and 3-aminophenylacetylene. Further, benzylamine, 2-amino-benzylamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,10-diaminodecane, 2,7-diaminofluorene, 1,4-diaminocyclohexane, 9,10 -Diaminophenanthrene, 1,4-diaminopiperazine, p-phenylenediamine, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminobiphenyl, 4 , 4′-oxydianiline, fluorenetetraamine, tetraaminediphenyl ether, melamine and the like can also be used. Among these, aniline, methylamine and the like are preferable, and aniline is more preferable. Aniline has a phenyl group in the molecule, and the phenyl group further improves the heat resistance of the molded product.

  Moreover, it does not specifically limit as aldehyde used, Formaldehyde etc. are mentioned. Examples of formaldehydes include formalin, which is an aqueous solution of formaldehyde, and paraformaldehyde, trioxane, which are polymers thereof. The state of the aldehyde used is not limited to solid or liquid. In particular, paraformaldehyde is preferable because it is solid (powder) at room temperature.

  Theoretically, lignin, amines and aldehydes may be used in an equimolar amount (in a molar ratio, lignin: amines: aldehydes = 1: 1: 2). However, since amines and aldehydes react as side reactions, it is preferable to use amines and aldehydes excessively in order to sufficiently modify lignin. For example, the amine is used in a proportion of 3 to 20 mol, preferably 3 to 10 mol, and the aldehyde is 6 to 40 mol, preferably 6 to 20 mol, relative to 1 mol of lignin. Even if amines and aldehydes are used in excess, the excessive amount of amines, aldehydes, and by-products of amines and aldehydes react and are taken into the curing system, so that the effects of the present invention are achieved. Has little effect on

  The reaction temperature is preferably about 50 to 200 ° C, more preferably about 100 to 150 ° C. The reaction time is preferably about 5 minutes to 1 hour, more preferably about 20 minutes to 1 hour. The reaction of lignin, amines and aldehydes can be performed by a solventless method without using a solvent, and a step of removing the solvent after the reaction is not necessary. As a result, the modified lignin of the present invention can be produced by a simpler method. For example, Japanese Patent Application Laid-Open No. 2003-206390 describes an example of a benzoxazine cyclization reaction using a primary amine and formalin, which has nothing to do with the use of lignin.

  Furthermore, the phenol resin molding material of the present invention (hereinafter sometimes simply referred to as “molding material”) contains a phenol resin and the modified lignin. The phenol resin is not particularly limited, and may be a novolak type or a resol type, and these may be used alone or in combination.

  The content of the phenol resin and the modified lignin contained in the molding material of the present invention is not particularly limited. For example, the modified lignin of the present invention is preferably contained in a proportion of 10 to 300 parts by mass, more preferably 20 to 200 parts by mass with respect to 100 parts by mass of the phenol resin. When the phenol resin and the modified lignin are contained in such a ratio, the viscosity of the molding material is hardly increased and the moldability is excellent, and the mechanical strength and water resistance of the obtained molded product can be further improved.

  The modified lignin is used, for example, in the form of a dry powder. The drying method is not particularly limited, and may be performed before or after powdering. For example, what is necessary is just to dry for about 20 minutes-2 hours at 50-150 degreeC using a drying furnace.

  The molding material of the present invention is generally composed of a filler, a curing agent (hexamethylenetetramine), a colorant, a plasticizer, a stabilizer, and a release agent (zinc stearate, metal soap, etc.) added to the phenol resin composition. An additive such as may be contained. The content of the additive is not particularly limited as long as it does not inhibit the effects of the present invention. For example, the filler is preferably 10 to 300 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the phenol resin. It is contained at a ratio of 200 parts by mass.

  The molding material of the present invention is processed into a molded product by a general molding method such as transfer molding or compression molding as in the case of ordinary thermosetting resins. The obtained molded product has excellent mechanical strength, water resistance, and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these Examples.

(Preparation of modified lignin having benzoxazine ring)
A herbaceous lignin having an average particle size of about 40 μm (containing 10% by mass of an H-type basic skeleton) was obtained from the waste liquid produced in the pulp production process using straw as a raw material. Next, the obtained herbaceous lignin, aniline and paraformaldehyde were charged into a reaction vessel so as to have a molar ratio of lignin: aniline: paraformaldehyde = 1: 10: 20. The reaction vessel was then held at 100 ° C. for 30 minutes.

The resulting reaction product (modified lignin), when analyzed by Fourier transform infrared spectroscopy (FT-IR), near 1360 cm ^-1 and near 1496 cm ^-1, appears characteristic absorption derived from the benzoxazine ring It was. Further, by differential scanning calorimetry (DSC) of the modified lignin, an exothermic peak due to a reaction not observed in the herbaceous lignin was observed. From the above analysis results, it was confirmed that herbaceous lignin was modified to lignin having a benzoxazine ring. In this way, a reactive modified lignin having a benzoxazine ring was obtained.

Example 1
300 parts by weight of novolak-type phenolic resin, 150 parts by weight of wood flour and 150 parts by weight of the modified lignin, 54 parts by weight of hexamethylenetetramine as a curing agent, and 4.5 parts by weight of zinc stearate as an internal release agent It mixed and knead | mixed for 3 minutes at 100-110 degreeC with 2 rolls, and the phenol resin molding material was obtained.

(Examples 2 and 3 and Comparative Examples 1 to 3)
A phenol resin molding material was obtained in the same manner as in Example 1 except that the components described in Table 1 were mixed in the proportions described in Table 1.

  The molding materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were molded using a transfer molding method at 170 ° C. for 15 minutes to obtain molded products.

<Moldability evaluation of molding materials>
The molding materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were examined for differential scanning calorimetry (DSC) behavior, melt viscoelastic behavior and thermogravimetric analysis (TG-DTA) behavior. As a result, no difference was observed in the curing characteristics, and the obtained phenol resin molding material was excellent in moldability regardless of whether or not it contains a modified lignin.

<Evaluation of physical properties of molded products>
About molded articles obtained using the molding materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3, (1) heat resistance, (2) mechanical strength, (3) electrical insulation, and (4) Water resistance was evaluated. The results are shown in Table 1.

(1) Heat resistance Heat resistance was evaluated by measuring the glass transition temperature (Tg) of the phenol resin molding material. First, solid dynamic viscoelasticity was measured using a DMS110 manufactured by SII Nanotechnology (frequency 1 Hz, temperature rising rate 2 ° C./min). The peak temperature of the tan δ curve obtained from the solid dynamic viscoelasticity measurement was defined as Tg.
(2) Mechanical strength Mechanical strength was evaluated by measuring bending strength. That is, in accordance with JIS K6911, the bending strength was measured at a crosshead speed of 3 mm / min and a span of 100 mm.
(3) Electrical insulation Electrical insulation was evaluated by measuring volume resistivity. That is, volume resistivity (Ω · cm) was measured using HP4339A manufactured by Yokogawa-Hewlett-Packard Co. according to JIS K6911.
(4) Water resistance Water resistance was evaluated by measuring water absorption. That is, the mass of the molded product and the mass of the molded product after being immersed in boiling water for 2 hours were measured, and the water absorption was calculated from the ratio. The lower the water absorption, the less water is absorbed and the better the water resistance.

  Example 1 using modified lignin has almost the same electrical insulation as Comparative Example 1 using unmodified lignin, but has good heat resistance and excellent mechanical strength and water resistance. It can be seen that

  Similarly, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 were also compared. It can be seen that Example 2 using modified lignin has better heat resistance and superior mechanical strength, electrical insulation and water resistance than Comparative Example 2 using unmodified lignin. Furthermore, Example 3 using modified lignin has almost the same heat resistance as Comparative Example 3 using unmodified lignin, but has excellent mechanical strength, electrical insulation and water resistance. Recognize.

Claims (11)

A modified lignin having a benzoxazine ring in the molecule ,
A modified lignin in which the oxazine ring portion of the benzoxazine ring is an oxazine ring formed by using 3 to 20 mol of amines and 6 to 40 mol of aldehydes with respect to 1 mol of lignin. The modified lignin according to claim 1, wherein the lignin before denaturation is derived from a herbaceous plant. The modified lignin according to claim 1 or 2 , wherein the lignin before modification contains an H-type basic skeleton in a proportion of 5% by mass or more. The modified lignin according to any one of claims 1 to 3 , wherein the amine is aniline. The modified lignin according to any one of claims 1 to 4 , wherein the aldehyde is paraformaldehyde. A phenol resin molding material containing the phenol resin and the modified lignin according to any one of claims 1 to 5 . The phenol resin molding material of Claim 6 which contains modified | denatured lignin in the ratio of 10-300 mass parts with respect to 100 mass parts of said phenol resins. A molded article obtained by molding the modified lignin-containing phenol resin molding material according to claim 6 or 7 . A method for producing a modified lignin having a benzoxazine ring in its molecule, comprising a step of reacting 3 to 20 mol of amines and 6 to 40 mol of aldehydes with respect to 1 mol of lignin. The production method according to claim 9 , wherein 3 to 10 mol of amines and 6 to 20 mol of aldehydes are used with respect to 1 mol of lignin. The production method according to claim 9 or 10 , wherein the lignin is lignin in a dry powder form.