JPH03130132A - Natural fiber reinforced molded product and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the strength of the product concerned and consequently decrease its thickness and, at the same time, reduce its weight by a method wherein pellets, each of which is prepared by bundling and solidifying a plurality of natural fibers, are mixed into the synthetic resin or ceramic molded product in order to strengthen the strength of the product. CONSTITUTION:The strength of the molded product concerned is strengthened by adding pellets 4, each of which is prepared by bundling and solidifying a plurality of natural fibers, into synthetic resin. Concretely, the product concerned consists of front surface rigid urethane resin layer 1, which was in contact with female mold, rear surface rigid urethane resin layer 2, which was in contact with male mold, foamed urethane resin layer 3 interposed between both said rigid urethane resin layers and pellets, which is made of natural fibers mixed into said foamed urethane resin layer by the predetermined mixing ratio. The mechanical load bearing capacity of the resultant rigid expandable urethane resin molded product becomes larger by the synergistic effect of urethane resin and pellet and consequently the strength of the product increases. Thus, the thinning of the molded product and the reduction of its weight are contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a natural fiber-reinforced molded product used for cases of electronic devices, etc., and a method for manufacturing the same.

[Conventional technology]

Today, synthetic resins (including synthetic rubber) are widely used in daily life and industry, but while they have many advantages, they have the disadvantage of lower mechanical strength and wear resistance than metals. . Ceramics are also widely applied due to their advantages, but! ! ! It has the disadvantage of being mechanically fragile.

The conventional technology of hard foamable urethane resin will be explained as an example of molded products of synthetic resins, ceramics, and the like.

In recent years, hard foamable urethane resin moldings have been widely used for cases of office automation equipment. This urethane resin molded product has the characteristics of moderate impact resistance, lightness, and good decorative properties, as well as the fact that the mold is simple and inexpensive, making it suitable for products produced in a wide variety of small quantities.

In other words, when manufacturing a rigid foamable urethane resin molded product, first, mix a hardening agent with foamable urethane resin and pour it into a female mold, and then turn the male mold into a female mold to obtain a predetermined shape. The opposing zero-foaming urethane resin generates heat due to reaction with the curing agent, becomes foamed, fills the mold, and is molded into a predetermined shape. In this case, it is sufficient for the mold to have enough strength to withstand the expansion force due to foaming of the urethane resin, and there is no need for a strong, high-precision mold like a conventional injection mold. Therefore, the mold can be produced relatively inexpensively.

[Problem to be solved by the invention]

However, molded products such as such hard foamable urethane resin molded products have a drawback that their strength and abrasion resistance are lower than those of metals and the like.

In particular, in a molded urethane resin molded product, both surfaces that were in contact with it are made of hard urethane resin, but the inside is made of foamable urethane resin, so the inside becomes mechanically weak and the overall strength is reduced. relatively low. As a result, when the case is molded, the thickness becomes thicker and the shape becomes larger in order to obtain the desired strength, and additional resin material is required.

In addition, glass fibers have been used as means for reinforcing the strength of molded products such as synthetic resins, but there are problems in that the manufacturing process is very complicated and costs are high.

[Means to solve the problem]

like this,! ! In order to solve the problem, the present invention uses synthetic fat-repellent and natural m! It is made by bundling up &ra pieces of I and mixing in assimilated berets to strengthen its strength.

In addition, we form a rim made by bundling multiple natural fibers, cut this rim into small pellets, mix the pellets with resin and ceramic, and pour them into a jar to produce a natural fiber-reinforced molded product. It is something.

In addition, we form an edge made by bundling multiple natural fibers, form a synthetic resin rod around this edge, cut it into small resin pellets, and pour this resin pellet into a mold to reinforce the natural fibers. It is used to manufacture molded products.

Alternatively, the pellet is treated with an isocyanate compound, mixed with a synthetic resin, and poured into a mold.

Additionally, the pellet is mechanochemically treated.

Further, the treatment with an isocyanate compound is carried out under pressure.

[For production]

In the present invention, since natural fibers are included in the molded product, the strength is increased due to the synergistic effect of the resin and natural fibers, and since the natural am is in the form of pellets rather than in pieces, it can be mixed into the width of the molded product. Easy to mix and mix evenly throughout.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of a hard foamable urethane resin molded product as an example of the natural m-penetration reinforced molded product according to the present invention, and FIG. 2 is an explanatory diagram of the molded product.

In these figures, ■ is hard urethane resin debris on the front surface that was in contact with the female mold, 2 is hard urethane resin debris on the back surface that was in contact with the male mold, and 3 is foaming between both hard urethane resin layers. The urethane resin waste 4 is a pellet made of natural HAM mixed in a predetermined ratio in this foamed urethane resin layer. A molded product made of such hard foamable urethane resin rri' has a greater strength against mechanical loads due to the synergistic effect of the urethane resin and the pellets, and therefore has increased strength. It is smaller than.

In FIG. 2, 5 is a female mold, 6 is a male mold, 7 is a discharge port through which the urethane resin containing a curing agent flows, and 8 is a discharge port from which the pellets 4 are discharged. The urethane resin is poured from the discharge lower into the female mold 5F, and at this time, the pellets 4 are dropped from the discharge port 8 by controlling the urethane resin at a predetermined ratio. pellet 4
After pouring the mixed urethane resin over the entire surface of the female mold 5, the male mold 6 is lowered to face the female mold 5 at a predetermined distance. At this time, there is a partial gap between both molds and the urethane resin. Eventually, the urethane resin generates heat due to the reaction with the curing agent, foams, and expands, filling both molds and being molded.

Since the pellets 4 are solid, they blend well into the urethane resin and are mixed smoothly.

If the fibers are mixed into the resin as they are, the mta will partially clump together and will not be uniformly distributed, making it impossible to obtain the desired strength.

Next, pellets will be explained in detail.

Natural fibers used as raw materials include the bast of plants such as kozo and santoku, the petioles and veins of plants such as sisal, the fruits of plants such as cotton, and the wood fibers of wood such as pine and beech. Animal excreta such as raw silk are used.

The following three methods are conceivable for making these natural wisps into pellets.

(1) After the fiber raw material is once made into paper in the same manner as in a normal paper manufacturing method, it is twisted into a bell body, which is then cut into pellets.

(2) Twisting the fiber material directly into a bell body,
Cut this into pellets.

(3) After cracking the fiber raw material, twist it into a bell body and cut it into pellets.

In either method, before cutting the bell body, the sliding surface is coated with a urethane-based resin that does not chemically react with the urethane resin that is the main molding material and is compatible with the urethane resin. . As a result, the pellets can be solidified, the pellets can be easily mixed into the urethane resin during molding, and the pellets can evenly spread to the end of the mold.

Pellets made of such natural fibers are made of glass ram.
Because it is very light compared to other materials, the molded product will be light even if the pellet content is high.

In addition, if a conductive material such as aluminum or carbon is mixed with the coating resin, the molded product will become conductive and
When used in the case of an im child device, it has a shielding effect against electromagnetic waves and electric fields.

Next, an example actually made will be explained.

"Example 1" When cord was used as a natural fiber and pellets with a l* diameter of about 0.3 mm and a length of about 5 mm were mixed into urethane resin at a ratio of 17 to 17 and 0.5%, Tensile strength (JIS K7113) is approximately 30 compared to conventional products that do not contain natural fibers.
% improvement, and the scratching strength (JIS K?203) is approximately 15
% headed.

The diameter of the pellet is selected from 0.1 to 0.5 mm, and the length is selected from approximately 1 to 10 cm, depending on the size and purpose of the molded product. In the case of urethane resin molding, the length is preferably 1 to 5 mm.

"Example 2" Pellets obtained by cutting ram into 2 to 51 pieces were dried in an oven heated to about 60° C. for 2 hours. This pellet 5
0 g, crude diphenylmethane diisocyanate (MDI
) 300g, approximately 500mM abrasive (3-5mm)
At the same time, excess MDI attached to the zero fiber pellets was placed in a bowl mill type grinder (barrel polishing machine) with a capacity of 15 fL and subjected to mechanochemical reaction treatment for about 24 hours.
was removed by washing with an inert solvent.

Next, 100 parts of polypropylene-added polyether polyol with a molecular weight of 700, and 1.5 parts of surfactant silicone oil.
A mixture of 15 parts of the treated fiber pellets and 0.1 part of dibutyltin dilaurate catalyst was prepared. Then, after quickly mixing 1105 parts of crude MD into all the scales of this mixed liquid and stirring at high speed, it was poured into a 71J (JIS K1113 type 1) prepared in advance to make a test piece, and a urethane resin molded test piece was prepared. was produced. Tensile strength was measured after being left for one week.

"Example 3" I fibers were cut into pellets of 2 to 5 squares and dried in an oven heated to about 60°C for 2 hours. 50g of this pellet
, crude diphenylmethane diisocyanate (MDI) 1
00g was placed in an autoclave and stirred for about 2 hours under a pressure of 7 kg/am. Excess MDI adhering to the am pellet was removed by washing with an inert solvent.

Next, 100 parts of polypropylene-added polyether polyol with a molecular weight of 700, and 1.5 parts of surfactant silicone oil.
A mixture of 15 parts of the treated fiber pellets and 0.1 part of dibutyltin dilaurate catalyst was prepared. Then, 5 parts of crude MDIIQ was quickly mixed into the entire mixed solution, stirred at high speed, and then poured into a mold for making test pieces (JIS K7113 type 1) prepared in advance to form urethane resin molded test pieces. Manufactured. Tensile strength was measured after being left for one week.

Further, as a comparative example, a urethane resin test piece containing no fibers was prepared using the same formulation and treatment as in Example 2, and the tensile strength was measured after leaving it for one week.

Below, Example 2. Example 3. The table shows the tensile strength of the three test pieces of the comparative example measured by the JIS K7113 test method.

As described above, in this example, by treating the natural fiber pellets with an organic isocyanate compound present when the pellets are ground, a urethane molded piece having an extremely effective reinforcing effect can be obtained. Moreover, even better effects can be obtained by performing this treatment under pressure.

In addition to using the pellets treated in this way by mixing them with the urethane composition liquid as in Example L, they can also be mixed and stirred into the isocyanate 14-part liquid and supplied to the urethane resin mold. , this is a highly preferred method. As the organic isocyanate compound that can be used, for example, all known compounds such as metaphenylene diisocyanate, tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, and naphthylene diisocyanate can be used.

Although urethane resin has been described in the above embodiments, it is of course applicable to various synthetic resins including other synthetic rubbers, and can also be mixed into fired ceramic powder and fired and molded. When applied to ceramics, even if fired at high temperatures, oxygen does not penetrate into the ceramic, so the natural fibers will not burn.

In addition, in the above examples, when mixing pellets into one synthetic resin, the finished pellets were mixed into the resin.
In the case of thermoplastic resin used for injection molding, the thermoplastic resin is molded into a rod shape with a long edge made of natural fibers as it is, and this rod-shaped resin is cut to a predetermined length. It is also possible to produce resin pellets. When these resin pellets are used as ordinary material pellets and poured into a mold, the resin becomes the main material and the natural fiber pellets are mixed in [reinforced synthetic resin as shown in Figure 1]. Molded products can be made. In this example, there is no need to cut the edges of the natural am, and the resin pellets containing fibers can be handled in exactly the same way as in a normal injection molding process, resulting in good workability.

The present molded product can be widely applied to transportation equipment such as automobiles and other fields in addition to the electronic devices listed in L.

〔Effect of the invention〕

As explained above, according to the natural fiber-reinforced molded product according to the present invention, since the natural fiber pellets are internally reinforced, the strength is significantly improved, the thickness of the molded product can be reduced, and the π amount It also becomes lighter.

In addition, since the natural 1a fibers are pelletized and then mixed into the molded product, it is possible to evenly distribute and mix sufficient natural fibers throughout the molded product.

Additionally, if a conductive material such as aluminum or carbon is mixed with the treated natural mm pellets at the same time, the molded product will become conductive and will have a shielding effect against electromagnetic waves and electric fields when used in the case of electronic devices. It becomes like this.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of one embodiment of the natural fiber reinforced molded product according to the present invention, and Fig. 2 is a view of the molded product 1J! It is a diagram. 1.2... Hard urethane tree layer, 3... Foaming urethane resin layer, 4... Pellet, 5... Female mold, 6...
・Male type, 7, 8...Discharge port. Funeral map 2nd figure

Claims (1)

[Claims] (1) A natural fiber-reinforced molded product in which strength is reinforced by mixing pellets made by bundling and solidifying a plurality of natural fibers inside a synthetic resin. (2) The feature is that it includes the steps of forming a wire body by bundling a plurality of natural fibers, cutting the wire body into small pellets, and mixing the pellets with synthetic resin and pouring them into a mold. A method for producing a natural fiber reinforced molded article. (3) A process of forming a wire body by bundling a plurality of natural fibers, a process of forming a synthetic resin into a rod shape around this wire body, and then cutting it into small resin pellets, and a process of molding the resin pellets. A method for producing a natural fiber-reinforced molded product, comprising the step of pouring into a molded product. (4) The natural fiber-reinforced molded article according to claim 1, in which the synthetic resin is made of ceramic. (5) A method for producing a natural fiber-reinforced molded article according to claim 2, in which the synthetic resin is made of ceramic. (6) A method for producing a natural fiber-reinforced molded article according to claim 2, wherein the pellets are treated with an isocyanate compound and then mixed with a synthetic resin, and the synthetic resin is a urethane resin. (7) The method for producing a natural fiber-reinforced molded product according to claim 6, wherein the pellets are further mechanochemically treated. (8) A method for producing a natural fiber-reinforced molded article according to claim 6, wherein the pellets are treated under pressure.