JP2019108490A - Composition for heat hardening and manufacturing method of heat hardening plastic - Google Patents

Abstract

To provide a cured article by a direct reaction with an epoxy compound from poor soluble lignin.SOLUTION: There is provided a resin composition for heat hardening containing a liquid article by dissolving modified lignin chemically modified by polyethylene glycol in alcohol, and an epoxy compound. By heating the resin composition for heat hardening to remove an alcohol component, then curing, a heat hardening plastic can be manufactured.SELECTED DRAWING: None

Description

  The present invention relates to a composition for heat curing and a method for producing a thermosetting plastic.

  Plastic materials are mainly synthesized from petroleum, but in order to meet the recent needs for reducing carbon dioxide emissions, synthesis from various biomass sources is also being attempted. Lignin is a component that occupies 20 to 30% of wood, and although it is obtained in large amounts from thinning and papermaking processes, it has not been used as a basic polymer material for industrial products. This is mainly because lignin is a large molecule with a complicated structure and individual differences among wood species, and the cost is high as a raw material for large scale chemical products due to the difficulty of separation and purification.

  In recent years, acid hydrolysis treatment of wood raw materials using polyethylene glycol as a solvent, which is different from conventional methods, makes it easier to extract lignin components that are relatively homogeneous as modified lignin, and continuous as powdered organic compound raw materials Examples have been found that can be supplied.

  The modified lignin can produce a thermosetting lignin-derived epoxy resin by polymerization with an epoxy compound by utilizing its hydroxyl group in the same manner as conventional lignin. On the other hand, modified lignin is characterized by being easily liquefied by a solvent or the like as compared with conventional lignin, and the same epoxy resin can be produced more easily.

  Although the preparation thereof has been attempted so far, lignin obtained from wood by a common alkaline digestion method and lignin sulfonic acid obtained by a paper-making process can be dissolved in a safe and versatile organic solvent commonly used. It is almost difficult to melt even with heat, and various raw material pretreatments, special solvents, and separation and purification methods have been studied for extraction as plastic raw materials. For example, lignin is finely pulverized by steam explosion and only low-molecular-weight lignin is extracted to be easily dissolved in a solvent, and then polymerization with an epoxy compound is performed (Patent Document 1). Furthermore, lignophenol is synthesized and separated by reaction with lignin obtained by alkaline digestion with phenol, and an epoxy resin is produced by reaction with epichlorohydrin (Patent Document 2). Both of them are examples of liquefaction of lignin and epoxy resinification, but there are big problems in process complexity and environmental impact of chemicals used.

  The present inventors took advantage of the fact that modified lignin is easily separated and purified by the use of polyethylene glycol with low environmental load, and again the safety of ethylene glycol systems having the same polyethylene glycol or similar structure We have found an example of making a thermosetting plastic by curing it with high solubility in organic solvents and curing it with an epoxy compound that is industrially versatile.

  However, in this method, in order to dissolve the modified lignin in the polyethylene glycol organic solvent sufficiently, it is necessary to carry out heating at 120 ° C. or higher and stir for 4 hours or longer. In addition, when performing molding processing by hand lay-up method or vacuum impregnation method using a mixture with an epoxy compound, it is necessary to keep the temperature at a temperature of 120 ° C. or higher in order to maintain the fluidity of the mixture If the temperature is raised too much in order to obtain sufficient fluidity, there is a process difficulty in which curing proceeds in the middle of the molding process. In addition, since the boiling point of polyethylene glycol is higher than the curing temperature with the epoxy compound, unreacted polyethylene glycol remains in the cured product, and the curing time takes 60 hours or more without a catalyst, and reduces the strength of the plastic. There was a problem.

  In addition, the present inventors dissolve and liquefy modified lignin in an industrially widely used organic solvent (dimethylformamide, DMF), further mix it with an epoxy compound, remove the organic solvent by drying, and temporarily cure it. We have also found a method characterized by later heat curing.

  However, a general-purpose organic solvent such as DMF is a high boiling point solvent that dissolves modified lignin easily at room temperature, and is 150 ° C. or higher, which is higher than the curing temperature with epoxy compound, to completely remove the solvent. It is necessary to use a high temperature, and there are molding difficulties such as distortion of resin due to simultaneous progress of solvent removal and curing. In addition, there are problems with environmental impact and safety with DMF and the like.

  As described above, in the technology for obtaining thermosetting plastics from modified lignin, the process should be further complicated due to the high dissolution temperature and the high solvent removal temperature, and the environmental load of chemicals used should be improved. There are challenges left.

JP, 2013-221113, A JP 2011-99083 A

  In the present invention, for effective utilization of lignin as a woody biomass material, a cured product is obtained by direct reaction of modified lignin with an epoxy compound, simple lignin dissolution method and solvent removal method therefor, and subsequent treatment The aim is to find the curing conditions.

The present invention provides the following inventions in order to solve the above-mentioned problems.
(1) A lignin composition comprising a lignin liquid composition or a lignin solid composition in which modified lignin chemically modified with polyethylene glycol is dissolved in alcohol.
(2) A lignin liquid composition obtained by dissolving modified lignin chemically modified with polyethylene glycol with alcohol or a resin composition for heat curing comprising a solid lignin composition and an epoxy compound.
(3) A method for producing a liquid resin composition for heat curing, which comprises heating and mixing the lignin solid composition according to (2) and the epoxy compound to form a liquid resin composition for heat curing.
The manufacturing method of the solid resin composition for heat-hardening which cools the liquid resin composition for heat-hardening as described in (4) and (3), and creates the solid resin composition for heat-hardening.
(5) A method for producing a thermosetting plastic comprising heating and melting again the solid resin composition for heat curing described in (4), curing with a mold and then curing to produce a thermosetting plastic. .
(6) A method for producing a thermosetting plastic, comprising forming the thermosetting resin by curing the solid resin composition for heat curing described in (4) as it is by heating and pressing.
(7) A raw material composition for a fiber reinforced thermosetting plastic, which comprises an artificial fiber blended with the resin composition for heat curing described in (2).
(8) A liquid or solid composition for heat curing as described in (3) or (4) is mixed with an artificial fiber and solidified by cooling to obtain a raw material composition for a fiber reinforced thermosetting plastic. A method for producing a raw material composition for fiber reinforced thermosetting plastic.
(9) A method for producing a fiber-reinforced thermosetting plastic, comprising mixing the liquid or solid resin composition for heat curing according to (3) or (4) with an artificial fiber and then heat curing.

  In the present invention, the modified lignin used is not soluble at room temperature, but it was found that the solubility in an alcoholic solvent is increased by heating preferably near the boiling point, so that the liquid of the modified lignin can be easily This method is characterized in that the preparation efficiency of a thermosetting plastic resin liquid is greatly improved by creating a state which is easy to mix with an industrially general-purpose epoxy compound. In addition, by providing a large difference between the thermosetting temperature of the resin and the removal temperature of the solvent, it is possible to sufficiently transfer the solvent and then shift to the process of the thermal curing, which makes the molding process easy and diverse Method. Furthermore, by heating and dissolving lignin using alcohol of poor solvent, it is possible to separate lignin, which has become easily mixed with the epoxy compound by cooling, as a solid, and it is excessive even without relying on evaporation alone. This method is characterized in that solvent alcohol can be easily recovered, removed, and reused.

Example 1 illustrates the process of obtaining lignin solids made in ethanol. In Example 3, the melting condition and hardness of the resin composition for heat curing are shown.

  The present invention does not require a high boiling point organic solvent as compared with the prior art, and the mixing of the modified lignin with the alcohol solvent and the epoxy compound is completed at a low temperature and in a short time, thus significantly reducing the time from the conventional method Can be In addition, since alcohol solvents can be removed by a simple solid-liquid separation method and drying at low temperature, there are advantages in saving process and environmental safety.

  In addition, the present invention is characterized in that it can be mixed with an epoxy compound at 100 ° C. or less to form an uncured mixture after obtaining a modified lignin solid containing the solvent after mixing with an alcohol solvent. Also provided is a method of having. Compared with the prior art, it is not necessary to mix modified lignin, solvent and epoxy compound preferably at 100 ° C. or higher, and the uncured mixture can be stored at room temperature, so that the heating and mixing temperature is high. Process saving is superior to conventional methods that must be used up immediately after mixing of liquids.

  Furthermore, since the separation and removal of the alcohol is easy while maintaining good mixing of the modified lignin and the epoxy compound, the ratio of the modified lignin and the epoxy compound can be easily adjusted, and the modified lignin is 50% or more Enables the preparation of high lignin containing epoxy resins.

  Also, compared to the prior art, it is possible to obtain a solid of the mixture before curing since most of the solvent can be removed at a temperature lower than the curing temperature of the epoxy. Therefore, it is possible to make a prepreg in which various artificial fibers are impregnated with the uncured mixture. In addition, this prepreg or a laminate of an uncured mixture solid and an artificial fiber fabric can be processed by heat molding, and has a process-saving property compared to the hand lay-up method and the vacuum impregnation method.

  The resin composition for heat curing of the present invention comprises a lignin liquid obtained by dissolving modified lignin chemically modified with polyethylene glycol with alcohol, or a solid lignin composition obtained by aggregation / separation and an epoxy compound. The heat-curing resin composition preferably further comprises a curing accelerator. At the time of dissolution and mixing, it is preferable to use a stirring device equipped with a stirring blade, a shaking stirring device, a homogenizer and the like.

  As the modified lignin used in the present invention, one in which a polyethylene glycol chain is bound to the backbone of lignin is used. As a method of coupling a polyethylene glycol chain to lignin, a method of derivatization using polyethylene glycol having an epoxy group, a method of dissolving polyethylene glycol in black liquor containing lignin and treating it, an acid solvant using polyethylene glycol as a medium Although the decomposition method is exemplified, in the present invention, modified lignin obtained by the acid solvolysis method is suitably used. The molecular weight of polyethylene glycol used for the reaction here is 100 to 1000, preferably 200 to 600. Plant biomass which is a raw material for producing modified lignin is not particularly limited. Softwoods such as cedar and cypress, hardwoods such as hippopotamus and Mizunara, or herbaceous biomass such as rice straw, bagasse and bamboo Is used. The acid solvolysis is preferably carried out by adding about 5 times by weight polyethylene glycol and 0.1 to 0.9% sulfuric acid based on polyethylene glycol to the chip or crushed material of these plant biomass, and at 60 ° to 90 minutes at about 140 ° C. It is done by heating. After dilution of the reaction with preferably 0.1 to 0.2 M dilute sodium hydroxide solution, the undissolved pulp components are removed by filtration and the filtrate is acidified with sulfuric acid or the like to form a precipitate. The material from which the precipitate is removed by filtration or centrifugation is used as modified lignin.

  The modified lignin modified with polyethylene glycol may be a modified lignin further having a polar group added. The polar group is preferably a carboxyl group, an amino group or a hydroxyl group, more preferably a carboxyl group.

  Epoxy compounds used in the present invention include aliphatic compounds such as epoxidized soybean oil and alkylene-1,6-diepoxy; bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy Resin, etc. may be mentioned. These epoxy compounds can be used alone or in combination of two or more.

  The curing accelerator used in the present invention may be any curing accelerator of epoxy resin, and, for example, 1,5-diazabicyclo (4,3,0) -nonene-5 (common name DBN) or 1,8 -Using a tertiary amine or tertiary amine salt such as diazabicyclo (5,4,0) -undecene-7 (common name DBU), an imidazole compound such as 2-ethyl-4-methylimidazole, triphenylphosphine or phosphonium salt Good. The weight ratio of the curing accelerator to the total solid when used is less than 20% by weight, preferably 0.1 to 10% by weight.

  In the present invention, alcohol is used as an organic solvent which dissolves modified lignin under heating. The alcohol may have a boiling point lower than the curing temperature of the epoxy resin, methanol (boiling point: about 64 ° C.), ethanol (boiling point: about 78 ° C. 9, 1-propanol (boiling point: about 97 ° C.), 2-propanol (boiling point: about 82 ° C), 1-butanol (boiling point: about 117 ° C), 2-butanol (boiling point: about 100 ° C), isobutanol (boiling point: about 108 ° C), t-butanol (boiling point: about) Alcohols having a carbon number of 5 or less, such as 83 ° C., etc., may be mentioned, among which methanol, ethanol and 2-propanol are preferable from the viewpoint of solubility, easiness of removal, safety and the like.

  The mixing weight ratio of modified lignin and alcohol is preferably in the range of 50 parts by weight to 50 parts by weight to 50 parts by weight to 20 parts by weight.

  In one embodiment of the present invention, the thermosetting plastic of the present invention is obtained by removing the residual alcohol content by heating the above-mentioned resin composition for heat curing, and then curing it. By heating, the hydroxyl group in the modified lignin molecule and the epoxy group in the epoxy compound molecule react directly with each other to polymerize and cure. The heating is usually selected at 50 to 200 ° C, preferably 80 to 150 ° C, for about 2 to 60 hours. A thermosetting plastic having a pencil hardness of HB or more can be obtained by curing treatment at 80 ° C. to 150 ° C. for about 2 to 60 hours.

  In one embodiment of the present invention, specifically, once modified lignin is dissolved in an alcohol solvent heated to 80 ° C. or less, it becomes easy to be mixed in a liquid phase with a general-purpose epoxy compound. Found out. After the resin composition mixed and liquefied in this manner is put into a mold, the heating temperature is gradually raised to evaporate the residual solvent, and the temperature is further raised to the curing temperature to be heat-cured.

  In another embodiment of the present invention, the solid lignin composition of the present invention is coagulated with alcohol, which is prepared by flocculation and separation after dissolving modified lignin chemically modified with polyethylene glycol in alcohol. It is a solid substance of lignin. Further, in another embodiment of the present invention, the heat-curable resin composition of the present invention comprises the solid lignin composition and an epoxy compound, and the heat-curable resin composition is heated. Removal of excess alcohol followed by curing provides a process for making thermosetting plastics.

  For example, lignin solids are coagulated by dissolving modified lignin with alcohol solvent and then cooling once, and the remaining free alcohol system is removed by simple separation and recovered as lignin solids containing alcohol, It mixes with a general purpose epoxy compound at 100 degrees C or less, and the liquid or solid unhardened mixture which consists of a modified lignin and an epoxy compound in which the residual amount of alcohol was suppressed is obtained. The unreacted mixture is molded and heat treated to obtain a cured resin.

  The uncured mixture of the modified lignin and the epoxy compound in the stage where most of the alcohol has been removed can be provided as a raw material that can be stocked until just before molding and heat curing since the curing temperature of the epoxy compound has not been reached. And the process of curing can be made separate, which can make the process of plastic production more efficient.

The raw material composition for fiber reinforced thermosetting plastics formed by mix | blending an artificial fiber with the resin composition for thermosetting of this invention can be obtained.
A fiber-reinforced biomass plastic material is provided by impregnating an uncured mixture of a liquid with an artificial fiber such as glass fiber, carbon fiber, polypropylene fiber, etc. and removing the alcohol solvent by heating gradually to cure it. obtain. Furthermore, it is possible to provide a resin plate obtained by subjecting a solid uncured mixture to heat compression molding as it is, and furthermore, a fiber reinforced biomass plastic material obtained by laminating the uncured mixture of an artificial fiber and a solid and subjecting it to heat compression.

  That is, a resin composition for heat curing comprising a liquid obtained by dissolving modified lignin in alcohol and an epoxy compound, or a solid lignin composition comprising modified lignin chemically modified with polyethylene glycol and an alcohol A heat-curing resin composition comprising a substance and an epoxy compound may be mixed with an artificial fiber and then heat-cured to produce a fiber-reinforced thermosetting plastic.

  Furthermore, a fiber-reinforced thermosetting plastic can be produced by laminating the heat-curing resin composition described above and an artificial fiber, and performing heat and pressure treatment to perform molding and curing.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited at all by these examples.

As modified lignin, one obtained by an acid hydrolysis / solvation method using polyethylene glycol having a molecular weight of 200 as a solvent was used. Commercial ethanol (special grade) was used as a solvent for dissolving the modified lignin, and bisphenol A was used as the epoxy compound.
Example 1: Lignin solid prepared in ethanol As shown in FIG. 1, when a large excess of ethanol was mixed with modified lignin powder and stirred, no reaction occurred at room temperature and lignin powder precipitated. When the temperature was raised to 70 ° C., the modified lignin gradually dissolved and became dark and liquid. When cooled to room temperature, the modified lignin began to flocculate, and it was possible to obtain a highly viscous dumpling-like mass separated from ethanol. The ethanol was removed by decantation to remove the mass and a solid of lignin could be obtained. When this lignin solid was heated at about 80 ° C. with a bisphenol A-type epoxy compound, a highly fluid liquid mixture could be obtained again in a few minutes.
Example 2: Plastic made from lignin solids and epoxy compounds

The lignin solid prepared in the same manner as in Example 1 is mixed with an epoxy compound at 100 ° C. in a proportion of 50 to 100% by weight, poured into an aluminum mold and heat cured overnight at 120 ° C. If the proportion of lignin is too high as in 1, it does not cure and does not cure and resin can not be produced, but it is possible to produce an epoxy resin with a high proportion of lignin of around 50% to 70%. , A hard hardness of up to 82 Shore hardness could be obtained.

Example 3 Preparation of Stockable Uncured Resin Composition A lump of ethanol containing lignin lumps prepared by melting after melting at 80 ° C. in ethanol as in Example 1 and having a Shore hardness of 1 to 7 It was a soft solid and could be stocked as a solid. This mass is mixed with bisphenol A at a weight ratio of 1: 1 to lignin, and heating is continued at 100 ° C., and the remaining ethanol is gradually evaporated, and the viscosity gradually decreases, and from modified lignin and bisphenol A The resulting solid mixture was obtained. When this solid was cooled and taken out once, it had a Shore hardness of around 20. The solid was placed in an aluminum mold and heated at 120 ° C. overnight to remelt and then form into an aluminum mold which was cured to give a hard plastic with a Shore hardness of 78. After curing, it was cooled once and then heated again at 120 ° C. This time it did not melt. From the above, it has been found that both lignin solids produced in ethanol and resin compositions before curing produced by mixing with an epoxy compound can be made and stored in the solid state.
Example 4: Preparation of fiber reinforced composite plastic

A liquid consisting of modified lignin and bisphenol A prepared by mixing a lump of dumpling-like lignin containing ethanol prepared as in Example 1 with bisphenol A at a weight ratio of 1: 1 with lignin and heating at 80 ° C. Were impregnated with glass fiber fabric and heated at 120 ° C. overnight to obtain a glass fiber composite epoxy cured product.

  The thermosetting plastic of the present invention can be used for effective utilization of woody biomass resources as a plastic member for home appliances, automobiles, OA equipment, further as a sealing material for piping, an adhesive sheet and the like.

Claims (9)

  A lignin composition comprising a lignin liquid composition or a lignin solid composition in which a modified lignin chemically modified with polyethylene glycol is dissolved in alcohol.   A lignin liquid composition obtained by dissolving modified lignin chemically modified with polyethylene glycol with alcohol or a resin composition for heat curing comprising a lignin solid composition and an epoxy compound.   A method for producing a liquid resin composition for heat curing, which comprises heating and mixing the lignin solid composition according to claim 2 and an epoxy compound to prepare a liquid resin composition for heat curing.   The manufacturing method of the solid resin composition for heat-hardening which cools the liquid resin composition for heat-hardening of Claim 3, and creates the solid resin composition for heat-hardening.   A method for producing a thermosetting plastic, comprising heating and remelting the solid resin composition for heat curing according to claim 4 and curing after molding with a mold to form a thermosetting plastic.   A method for producing a thermosetting plastic, comprising curing the heat-curing solid resin composition according to claim 4 as it is by heating and pressing and curing to form a thermosetting plastic.   The raw material composition for fiber reinforced thermosetting plastics which mix | blends an artificial fiber with the resin composition for heat-hardening of Claim 2.   A fiber-reinforced thermosetting resin composition characterized in that the heat-curing liquid or solid composition according to claim 3 is mixed with an artificial fiber and solidified by cooling to obtain a raw material composition for a fiber-reinforced thermosetting plastic. The manufacturing method of the raw material composition for plastics.   A method for producing a fiber-reinforced thermosetting plastic, comprising mixing the liquid or solid resin composition for heat curing according to claim 3 with an artificial fiber and then heat curing.