JPS63270102A - Ligneous fiber molded body and its manufacture - Google Patents

Abstract

PURPOSE:To process the title molded body by deforming further after primary molding, by a method wherein an ethylene vinyl alcohol copolymer whose ethylene molar ratio and a degree of saponification are specific is regarded as a first ingredient, the other thermoplastic resin is regarded as a second ingredient, a composite fiber where the first ingredient occupies a specific percent and covers a fiber surface and ligneous fiber are mixed up with each other at a specific ratio and the whole is unified through adhesion by the composite fiber. CONSTITUTION:An ethylene vinyl alcohol copolymer whose ethylene molar ratio (Emol.%) is 20<=E<60 and degree of saponification is 98% or higher is regarded as a first ingredient and the other thermoplastic resin is regarded as a second ingredient. A composite fiber where the first ingredient amounts to at least 20wt.% and covers at least a part of a fiber surface and a ligneous fiber are mixed up with each other at a weight ratio of 1:99-50:50. A ligneous fiber molded body adhering the ligneous fibers with the composite fiber is manufactured by heating the ligneous fibers at a heating temperature T deg.C falling within a range of T>=17E+51.5, T<-1.9E+245 and T<2.13E+79.4 while pressurizing them in the presence of water. A ligneous structural body is deformable as a secondary processing by performing compression and wet heat treatment of the same to which a primary molding has been performed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a wood fiber molded article used for building materials, furniture, automobile interior materials, etc. The present invention relates to a wood fiber molded article that can be further deformed and processed after being primarily formed, and a method for manufacturing the same.

(Prior Art) Wood fibers generally refer to wood, crushed materials such as wheat straw and coconut shells, pulp precursors, etc., and have a cross section of approximately 112 mm or less.1 Wood fibers are used as raw materials for synthetic wood.

Bonding wood fibers with adhesives such as thermosetting resins,
Alternatively, a technique is conventionally known in which thermoplastic fibers such as polyolefin fibers are mixed with wood fibers, the thermoplastic fibers are heated above their melting point to melt, and the wood fibers are bonded and integrated. (Unexamined Japanese Patent Publication No. 50-1181. Unexamined Japanese Patent Publication No. 52-
100591. (Unexamined Japanese Patent Publication No. 50-1182) (Problems to be Solved by the Invention) In such conventional technology, when thermosetting resin is used as an adhesive, it is extremely difficult to reshape it by heat pressing once it is completely cured. Have difficulty. Therefore, there is a method of suppressing the degree of hardening, leaving it as a semi-hardened product, and then re-molding it with heat press etc. to form the desired shape.
-144471) Semi-cured products need to be stored at room temperature, and side reactions that do not contribute to curing progress gradually, so care must be taken when storing them, and the performance is lower than that of products that are directly cured without being semi-cured. There was a tendency to Also, in terms of applications, those using thermosetting adhesives are extremely hard and have poor plasticity, so they were not used for anything other than hardboards such as building materials and furniture materials.

On the other hand, in the case where polyolefin fibers are bonded by heat-melting them, the mixture with wood fibers must be thoroughly dried to a moisture content of 10% or less; high moisture content may cause poor adhesion or uneven adhesion. Also, polyolefin polymers such as polyethylene and ethylene-vinyl acetate copolymer have poor adhesion to wood fibers, and unless they are added in a large amount (30% by weight or more), the molded product may not have sufficient plasticity or the cut surface may deteriorate. It had the disadvantage that it could cause deterioration.

(Means for Solving the Problems) The present inventors investigated the wet heat adhesive properties of fibers containing at least a portion of ethylene vinyl alcohol copolymer (hereinafter abbreviated as EVOH fibers), and found that when a certain amount or more The inventors have discovered that fibers containing vinyl alcohol in the polymer have good hydrophilicity and can be thermally bonded to wood fibers using water vapor, leading to the present invention.

That is, in the first aspect of the present invention, the ethylene molar ratio (E mol %) is 20≦E<60. The first component is an ethylene vinyl alcohol copolymer with a degree of saponification of 98% or more, the second component is another thermoplastic resin, and the first component is at least 20% by weight.
The composite fiber (EVOH fiber), in which the first component always occupies at least a part of the fiber surface, and the wood fiber are mixed in a weight ratio of 1=99 to 50:50.

This is a wood fiber molded product made entirely of adhesively integrated composite fibers.

The reason why the ethylene molar ratio (E%) of the EVOH fiber is required to be 20 or more is because the spinnability of the EVOH fiber is problematic. When E=20, the melting point of E'V OH is 20
7°C, and the temperature at which gelation begins after staying for 5 minutes or more is measured to be 240.2°C. To perform stable melt spinning within this range, a temperature at least 20°C higher than the melting point, that is, 227°C, is required, so there are two possible temperature ranges.
40.2-227.13.2 (°C), and while it is desirable to have at least this temperature range during melt spinning, there is a need for a wider temperature range for composite spinning with other thermoplastic polymerizable materials. This is because if it is too narrow, it is difficult to perform stable spinning.

Further, when E is large, the melting point of the EVOH fiber becomes low, but the hydrophilicity becomes poor. Therefore, in order to obtain the thermoadhesive fiber which is the object of the present invention, E is set to be less than 6.0. The reason why the degree of saponification of ethylene vinyl alcohol copolymer is 98% or more is 98%
If the temperature is lower, the molten resin will easily foam, resulting in more fiber breakage during the spinning process.Ethylene vinyl alcohol copolymer and other thermoplastic resins that make EVOH fibers are polypropylene.

Polybutylene terephthalate, nylon 6 and nylon 66 are conveniently used, and polyethylene terephthalate is also applicable. The reason for mixing these other thermoplastic resins is to improve the spinnability of EVOH fibers, and the higher the proportion of these other thermoplastic resins, the more stable the process will be.
The amount is at most 80%. If the ethylene vinyl alcohol content is less than 20%, the thermal adhesion properties, which are the intended use of EVOH fibers, will deteriorate.

However, if the process is carefully controlled by a skilled and talented engineer, EVOH9i fiber can be spun even with 100% ethylene vinyl alcohol copolymer (first component), and such EV (' Needless to say, H fibers have a strong wet heat bonding ability and can be favorably used as an adhesive for the wood fiber structure of the present invention.

EVOH fibers are mixed with wood fibers as adhesives,
The amount is 1 to 50% of the total weight of EVOH and wood fiber.
%. The smaller the amount of EV○H fiber, the softer the molded product will be, the more elastic it will be, and the more wood-like it will be. Conversely, the larger the amount of EVOH fiber, the harder the molded product will be, with a smoother surface and stronger strength. If EVOH14affl is less than 1%, the wet heat adhesion effect will be insufficient and the bending stress and abrasion resistance will be poor, making it impossible to put it into practical use. If the amount exceeds 50%, the molded product becomes rigid and loses its woody quality.

Next, a method for manufacturing such a wood fiber structure will be explained according to the second aspect of the present invention.

In the second aspect of the present invention, an ethylene vinyl alcohol copolymer having an ethylene molar ratio (E mol %) of 20≦E 60 and a degree of saponification of 98% or more is the first component, and another thermoplastic resin is the second component.
The weight ratio of the composite fiber and the wood fiber, in which the first component accounts for at least 20% by weight and the first component always occupies at least a part of the fiber surface, is 1=99 to 50:
Mix in a ratio of 50 parts and pressurize in the presence of moisture.
T≧178+51.5. T <-1.9E+245
．． This is a method for producing a wood fiber molded article in which wood fibers are bonded together using the conjugate fibers by heating to a heating temperature (T° C.) within the range of T<2.13E+79.4.

The melting point of the EVOH fiber used in the present invention is approximately (-1.9E
+245 > ℃, but even if EVOH fiber is below its melting point, in the presence of moisture, the surface will quickly swell and gel under the action of the water vapor generated by heating, allowing it to function as an adhesive fiber. Can be done. The temperature is (
1.17E+51.5) 'C or higher.

In addition, even if the temperature is below the melting point, if the temperature is too high, especially EVOH
If the amount of fiber is large, the temperature must be lower than (2,13E479.4)°C because it will stick to the heating plate or heating roll significantly.

The graph in Figure 1 shows the relationship between the ethylene molar ratio (E mol%) of the first component of EVOH fibers and the thermal adhesion temperature (T°C) of the nonwoven fabric. The temperature is within a range where this does not occur. Also EVOH
The temperature at which fibers can swell in the presence of moisture is (1.17E
+51.5) °C or higher, the shaded part of the graph is the temperature range in which bonding is possible.

In order to swell and gel the EVOH fibers and exhibit their adhesive function, moisture is required when the heating temperature is below the melting point as in the present invention, but for this purpose, approximately 8% moisture is added to the wood fibers to be bonded. This is possible if there is water in the water. If wood fibers are stored at room temperature, they usually contain about 10% moisture, so thermal bonding is possible as is, but to complete thermal bonding in a short time, a moisture content of about 15% or more is desirable. If the wood fiber is dry and the moisture content is less than 15%, it is sufficient to add some moisture.

The heating element can be a hot plate press, a continuous belt press, a microwave heating method, a dielectric heating method, an infrared heating method, etc., but in any case, the heated object is prevented from escaping the steam generated during heating. Therefore, both sides must be pressed with non-air permeable supports.

In addition, a mixture of wood fibers and EVOH fibers with a low density (apparent specific gravity of 0.4 or less) with a thickness of 1
If the material is larger than 1 cm, heat conduction is poor when thermocompression bonded using a heat press machine (and if the amount of EVOH fiber is small, sufficient peel strength may not be obtained in the plane parallel to the crimped surface. In such cases, By applying microwave heating while compressing with a breathable support plate, sufficient adhesive strength can be obtained inside.

If the surface hardness is insufficient after microwave heat treatment alone, a molded product with a smooth surface can be obtained by continuing heat pressing.

Furthermore, by stacking a plurality of mixed boards of wood fibers and EVOH fibers, compressing them, and subjecting them to moist heat treatment, it is possible to obtain an integrally molded product in which each layer is bonded.

In either case, the wood fiber molded article of the present invention, which is produced by subjecting EVOH fibers to a moist heat treatment to swell and exhibit adhesive ability, has moisture that turns into steam during the heat treatment, resulting in EVO
It is characterized by instantaneously swelling and gelling the H fibers, and in order to do this, the hot plate must be impermeable and sandwich the object to be heated to prevent water vapor from escaping.This is done by the hot plate. In addition to heating, the microwave heating method described above is used.

The same applies to the dielectric heating method.

Further, the press pressure may be any value that is suitable for the repulsive force during compression, but if a press pressure of 0.5 kg/cm2 or more is applied, a wood fiber structure with a specific gravity of approximately 0.4 or more can be obtained r).

(Function of the Invention) Such a wood fiber structure according to the present invention has the characteristic that it can be freely deformed as a secondary process by first forming it into a flat plate, for example, and then subjecting it to compression and moist heat treatment again.

Conventional thermosetting resins are troublesome to store if they are subjected to secondary processing, and polyolefin fibers are used in large quantities (approximately 30%
However, the essential fiber molded article according to the present invention, which is molded as a primary process, can be deformed 3 to 5 times by compressing it into a separate mold and reheating it. It was possible to mold into the desired shape without causing any cracks or peeling between layers.

(Example) EVOH fiber, E=38. MFR=40g/
A 10-minute ethylene vinyl alcohol copolymer was used as the first component, MFR = 55 g/10-minute polypropylene was used as the second component, and the component ratio was 50:50, with the first component in the sheath and the second component. The core composite fiber is melt-spun, drawn, and H! 1 machine crimping process at 110℃
After drying for a minute, the fibers were cut to obtain short cut fibers of 2 denier and 5 mm, which were used in the following examples.

(Examples 1 to 6. and Comparative Example 1.2) EVOH fibers and wood fibers were mixed in a dry weight ratio of 5:95, 10:90, and 30 near 0, and the basis weight (kg/ m2), 1.6.1.2. A mat with a moisture content of approximately 15% was prepared, and this was sandwiched between hot plates maintained at 120'C at a pressure of 13 and 2 (kg/c+s2), compressed to a thickness of 2.5 degrees, and heated at 120 °C for 5 minutes. ℃
I kept it. The resulting molded product was measured for fiber shedding rate due to bending stress and surface abrasion.

Bending stress: A bending test was conducted on a sample of 100 x 50 x 10 x 50 x 70 x 70 x 100 x 100 x 100 x 100 x 100 x 50 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 x 100 samples samples at a speed of 10 -/inch in accordance with JISA 1408.

Dropping rate: J I using samples of 80 dragons vertically and 40 dragons horizontally.
According to the S L -1004-5,16A method (universal type method), a flat abrasion test was performed 500 times under a load of 5 bonds using N[L250 abrasive paper, and calculation was made using a linear equation.

Weight before test - Mold weight after test Falling rate (%") = X100 Weight before test Next, a molded product with a mixing ratio of 0.5:99.5 was made in the same manner as a comparative example. The obtained results are shown in the table. -1.

Margin Table 1 Bending stress 50 kg/cs 2 or more, falling rate 10%
The following are practically required as a board. Weight: 1.6kg
,/m2, the bending stress is 10 even with 0.5% EVOH fiber.
．． Although it has a high weight of 5 kg/c+m, it cannot withstand use because the shedding rate is as high as 12%.

It was confirmed that even at the same mixing ratio, as the specific gravity decreases, the bending stress decreases, but the degree of deformation until breakage increases and the workability improves.

(Comparative Example 3.4) In the same manner as in the example, the mixing ratio was 10:90jO near 0. Create a mat with a moisture content of 15% and use it without using a hot plate.

It was heated with hot air at 120°C for 10 minutes. Although the moisture in the mat evaporated and the mat dried, the EVOH fibers did not exhibit sufficient adhesive strength and the bending stress was weak.

The surface was rough. Table 2 shows the results.

Table 2

[Brief explanation of drawings]

The drawing shows the ethylene molar ratio (E mol%) of the first component of the EVOH fiber used in the present invention and the wet heat bonding temperature (T
It is a graph showing the relationship 'C). Patent applicant: Daiwabo Co., Ltd. - 111 → E%

Claims (2)

[Claims] (1) Ethylene molar ratio (E mol%) is 20≦E<60,
An ethylene vinyl alcohol copolymer with a saponification degree of 98% or more is the first component, another thermoplastic resin is the second component, and the first component is
The component accounts for at least 20% by weight, and the first component always occupies at least a part of the fiber surface, the composite fiber and the wood fiber are mixed in a weight ratio of 1:99 to 50:50, A wood fiber molded article whose entire body is bonded and integrated with the composite fibers. (2) Ethylene molar ratio (E mol%) is 20≦E<60,
An ethylene vinyl alcohol copolymer with a saponification degree of 98% or more is the first component, another thermoplastic resin is the second component, and the first component is
Composite fibers in which the component accounts for at least 20% by weight and in which the first component always occupies at least a portion of the fiber surface are mixed with wood fibers in a weight ratio of 1:99 to 50:50, and the moisture is removed. T≧1.17E+5 while pressurizing in the presence of
1.5, T<-1.9E+245, T<2.13E+7
9. A method for producing a wood fiber molded article, which comprises heating to a heating temperature (T° C.) within the range of 9.4 and bonding wood fibers together using the conjugate fiber.