HK1166758B

HK1166758B - Molding material for extrusion foam molding, process for producing same, woody molded foam produced from the molding material, and process and apparatus for producing the woody molded foam

Info

Publication number: HK1166758B
Application number: HK12107381.8A
Authority: HK
Inventors: 武恭菊池; 和正守田; 浩二东; 雄一郎中村
Original assignee: 北京生生文化有限责任公司
Priority date: 2009-07-02
Filing date: 2010-05-13
Publication date: 2015-09-18

Description

Molding material for extrusion foam molding, method for producing same, wood foam molded body produced using molding material, and method and apparatus for producing wood foam molded body

Technical Field

The present invention relates to a molding material for extrusion foam molding containing a thermoplastic resin and wood powder as main components, a method for producing the same, a wooden foam molded body produced using the molding material, and a method and an apparatus for producing the wooden foam molded body.

Background

A molded article (wood molded article) obtained by forming a molded material (molded green land) obtained by melting and kneading a thermoplastic resin and wood powder into a desired shape has properties as a resin molded article such as a texture of wood and a low possibility of rotting, and is therefore widely used as a building material for a wood deck installed outdoors, for example.

An example of an extrusion molding apparatus used for producing such a wood molded body by extrusion molding is shown in fig. 8.

The extrusion molding apparatus 641 includes: an extruder 642 having a cylindrical barrel 643 and a screw 645 rotatably provided inside the barrel 643; a driving source (not shown) for rotating the screw 645 of the extruder 642; and a die 650 for introducing a molding material 625a extruded from an outlet 643a provided in a barrel 643 of the extruder 642 and molding the molding material 625 a.

In order to form a wooden molded body (plate material) by using the extrusion molding apparatus 641 having the above-described configuration, for example, a wooden molded body (plate material) having a cross-sectional shape matching the cross-sectional shape of the molding chamber 650a can be manufactured by feeding a necessary material such as wood flour, a thermoplastic resin, a pigment, a toughening agent, etc. mixed at a predetermined ratio as a raw material mixture into a barrel 643 of an extruder through a hopper 644 provided in the barrel 643, rotating a screw 645 of the extruder by a drive source, applying an extrusion force in the direction toward the tip end of the screw 645 to the raw material mixture while heating and kneading the raw material mixture, and extruding a molten and plasticized molding material 625a into the molding chamber 650a formed in the die 650 through an outlet 643a provided in the barrel 643 on the tip end side of the screw 645 (for example, refer to patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. Hei 8-118452

Technical problem to be solved by the invention

In the case where a mixed material containing a thermoplastic resin and wood flour as main components is formed into a predetermined shape by extrusion molding, as described above, the key point of the method is how to obtain a product with stable quality while improving productivity in the step, by forming a molding material 625a melt-kneaded by the extruder 642 into a desired shape in the die 650 and cooling and solidifying the molding material to form a target product.

However, in the case of producing a wood molded body containing a large amount of wood flour, it is difficult to control the flow of the molding material 625a, and it is difficult to achieve both improvement in productivity and production of a product having stable quality.

In particular, when a foaming agent is added to the raw material in order to foam the molten and plasticized molding material 625a into a woody molded article (referred to as a "woody molded article" in the present invention), the pressure and flow of the molding material 625a in the extruder 642 and the die 650 are drastically changed with the foaming of the foaming agent, pulsation is generated in the molding material 625a, and the like, and it is more difficult to control the flow of the molding material 625a, and bubble distribution unevenness and void are generated with the distribution unevenness of the foaming gas in the molding material 625a, and wrinkles are generated on the surface with the pulsation of the molding material 625a, and defects are easily generated in the finally obtained woody molded article, and it is more difficult to stably produce a product having no fluctuation in quality.

For example, when extrusion molding is performed using a known extrusion molding apparatus 641 described with reference to fig. 8, using a mixed material obtained by simply adding a foaming agent to the raw materials comprising wood flour, thermoplastic resin, pigment, toughening agent, etc., the foaming agent generates a foaming gas by heating during melt kneading in a cylinder 643 of an extruder 642, and the foaming gas expands to generate bubbles, and the bubbles thus generated tend to concentrate in the center of the molded material.

If the molding material 625a is cooled and solidified in the molding chamber 650a formed in the mold 650 in a state where the air bubbles are concentrated in the center portion of the molding material 625a as described above, the air bubbles are further concentrated in the center portion (core portion) in the width direction of the wood foam molded body, and therefore, an internal defect is generated due to a large internal void G having a size equal to or larger than a so-called "cavity", and therefore, the center portion in the width direction of the wood foam molded body expands in both thickness directions in the longitudinal direction, and a square cross section cannot be maintained, and a product cannot be obtained, and the strength is naturally reduced, and it is not commercially possible or very difficult in an experimental stage to manufacture a foam molded product having a high quality as in the case of no foam (fig. 9). In fig. 9, in order to maintain strength, a zigzag groove is formed in the lower side of the forming plate in the figure along the longitudinal direction.

In order to solve the above-described problem, for example, it is conceivable to cope with the problem by changing the configuration of one of the extrusion molding apparatuses 641, and for example, as shown in fig. 10, it is tried to arrange a perforated plate 652 at the inlet of a die 650, form a mesh made of a plurality of meshes by the perforated plate 652, extrude a molded material 625a into a molding chamber 650a of the die 650 through the meshes of the perforated plate 652, apply resistance to the molded material 625a, thereby increase the internal pressure of a tube 643, suppress expansion of a foaming gas inside the tube 643, make the molded material 625a more uniformly disperse a foaming gas in the tube 643 of an extruder 642, and then introduce such a molded material 625a into the die 650.

However, even when the wooden foam molded body is formed by the extrusion molding apparatus 641 having such a configuration, similarly to the case of using the known extrusion molding apparatus 641 shown in fig. 8, it is impossible to avoid a phenomenon in which bubbles are easily concentrated in the center portion (core portion) of the foam molded body molded in the molding chamber 650a, and it is impossible to avoid generation of the internal voids G shown in fig. 9, and it is difficult to obtain a wooden foam molded body having high strength.

As described above, in order to obtain a high-quality woody molded foam having no defects by extrusion molding, it is necessary to uniformly perform the flow of the molding material 625a and the diffusion of the foaming gas into the molding material 625a during extrusion molding and to appropriately perform the expansion of the molding material 625a by the foaming gas, but it is difficult to satisfactorily perform the control by merely changing the configuration of one side of the extrusion molding apparatus.

Disclosure of Invention

The present invention has been made to solve the above-described problems of the conventional techniques, and an object of the present invention is to provide a molding material for extrusion foam molding which can obtain a high-quality woody foam molded body by newly investigating the composition of one of the raw materials.

Further, it is another object of the present invention to provide a high-quality woody molded foam which is produced using the molding material and has no defects.

Further, another object of the present invention is to provide an extrusion molding apparatus and an extrusion molding method suitable for extrusion foam molding using the molding material for extrusion foam molding.

Technical scheme for solving technical problem

The following description will be made by adding reference numerals in the embodiments to the technical solutions for solving the problems. The reference numerals are used to clarify the correspondence between the description of the claims and the description of the embodiments, and are not, of course, intended to limit the technical scope of the claims of the present invention.

In order to solve the above problems, the molding material for extrusion foam molding of the present invention is used for manufacturing a wood foam molded body by adding a foaming agent during extrusion molding, and comprises wood flour and one or a mixture of polypropylene (PP), ABS resin and polyvinyl chloride (PVC) as a main component, or a mixture of wood flour, polypropylene (PP) and Polyethylene (PE) as a main component, and 1 to 5 wt% of alkane having a molecular weight of 300 to 1000g/mol, wherein the wood flour and one or a mixture of polypropylene (PP), ABS resin and polyvinyl chloride (PVC) are mixed in a ratio of: 50-55 wt% of wood flour, 45-50 wt% of one or a mixture of polypropylene (PP), ABS resin and polyvinyl chloride (PVC), or the mixture ratio of the wood flour to the mixture of the polypropylene (PP) and the Polyethylene (PE) is as follows: 50-55 wt% of wood flour, 45-50 wt% of a mixture of polypropylene (PP) and Polyethylene (PE), and 1 wt% or less of wood flour, wherein the wood flour is produced into particles with a specified particle size.

And a molding material for extrusion foam molding which is formed into pellets (ペレット) after melt kneading to uniformly disperse the respective components.

Further, the molding material may be: the mixture ratio of the wood powder and one or a mixture of polypropylene (PP), ABS resin and polyvinyl chloride (PVC) is as follows: 50-55 wt% of wood flour, 45-50 wt% of one or a mixture of polypropylene (PP), ABS resin and polyvinyl chloride (PVC), or the mixture ratio of the wood flour to the mixture of the polypropylene (PP) and the Polyethylene (PE) is as follows: the wood powder accounts for 50-55 wt%, and the mixture of polypropylene (PP) and Polyethylene (PE) accounts for 45-50 wt%.

Furthermore, the molding material may also contain fillers and/or toughening agents and/or pigments in addition to the wood flour, thermoplastic resin and alkane.

The present invention also relates to a woody molded foam obtained by extrusion-molding any of the above-mentioned molding materials together with a foaming agent into a predetermined shape by an extrusion molding apparatus, and a method for producing the woody molded foam.

The method for producing a woody molded foam is characterized in that any of the above-mentioned molding materials is introduced into a screw extruder 12 provided in an extrusion molding apparatus 11 together with a foaming agent, melt-kneaded at a temperature equal to or higher than the decomposition temperature of the foaming agent, the molding material 25a extruded from the extruder 12 is introduced into a molding chamber 31 of a molding die 30 while maintaining the molding material 25a in a pressurized state, the pressure of the molding material 25a is released when the molding material is introduced into the molding chamber 31 of the molding die 30 to foam the molding material 25a, and the molding material 25a is cooled and solidified while being molded into a shape corresponding to the cross-sectional shape of the molding chamber 31 in the process of passing through the molding chamber 31 of the molding die 30.

The method for producing the wood-based foamed molded article may include: an extrusion die 20 is provided between the extruder 12 and the molding die 30 of the extrusion molding apparatus 11, the extrusion die 20 is communicated between an outlet (an outlet 13a of the tube 13) of the extruder 12 and an inlet 30a of the molding die 30, resistance is applied to the molding material 25a introduced into the extrusion die 20 from the outlet 13a of the extruder 12 to increase the pressure of the molding material 25a in the extruder 12, and the flow path area of the extrusion die 20 is reduced from the inlet 20a side to the outlet 20b side of the extrusion die 20, so that the molding material 25a is introduced into the molding chamber 31 of the molding die 30 while maintaining the pressure of the molding material 25a introduced into the extrusion die 20 from the extruder 12, and the pressure of the molding material 25a passing through the extrusion die 20 is released when the molding material 25a passes through the outlet 20b of the extrusion die 20, the molding material 25a is foamed at the inlet 30a portion of the molding die 30.

An extrusion molding apparatus for manufacturing a wooden foam molded body by the method is characterized by comprising: a screw extruder 12 for melt-kneading a molding material and a foaming agent, which are introduced together and mainly contain wood flour, and one or a mixture of polypropylene (PP), ABS resin, and polyvinyl chloride (PVC) at a temperature equal to or higher than the decomposition temperature of the foaming agent, or for melt-kneading a molding material and a foaming agent, which are introduced together and mainly contain wood flour, and a mixture of polypropylene (PP) and Polyethylene (PE) at a temperature equal to or higher than the decomposition temperature of the foaming agent; an extrusion die 20 which communicates with the outlet 13a of the extruder 12 and into which the molded material extruded by the extruder 12 is introduced; and a forming die 30 which communicates with the outlet 20b of the extrusion die 20, and which introduces a molded material having passed through the extrusion die 20 into a molding chamber 31 formed inside the forming die 30, and which cools and solidifies the molded material 25a while molding the molded material 25a moving in the molding chamber 31 into a shape corresponding to the internal shape of the molding chamber 31, wherein a mesh-shaped perforated plate 22 is provided in a portion of the outlet 13a of the extruder 12, a plurality of holes are formed in the perforated plate 22, and a resistance material 26 is provided in the extrusion die 20, and the resistance material 26 reduces a flow path area in the extrusion die 20 from the inlet 20a side to the outlet 20b side of the extrusion die 20.

Preferably, the flow path area in the outlet of the extrusion die is smaller than the area of the inlet of the molding die.

The extrusion molding apparatus 11 may be: the outlet 20b of the extrusion die 20 and the inlet 30a of the molding chamber 31 of the molding die 30 have the same shape, the cross-sectional shape of the end portion (mandrel portion 26c) of the resistance member 26 on the molding die side is similar to the shape of the outlet of the extrusion die, the cross-sectional shape of the end portion (mandrel portion 26c) of the resistance member 26 on the molding die side is slightly smaller than the shape of the outlet of the extrusion die, and the end portion of the resistance member 26 on the molding die side is disposed at the center of the outlet 20b of the extrusion die 20.

Further, it is preferable that the screw extruder of the extrusion molding apparatus 11 is a twin-screw extruder.

Preferably, the MFR (melt flow rate) of one or a mixture of the polypropylene (PP), the ABS resin, and the polyvinyl chloride (PVC), or a mixture of the polypropylene (PP) and the Polyethylene (PE) is in the range of 0.5 to 10(g/10 min).

Effects of the invention

According to the above-described configuration, the present invention can obtain the following significant effects.

A high-quality woody foam molded body can be obtained by using, as a molding material for extrusion foam molding in the extrusion foam molding apparatus 11, a molding material for extrusion foam molding which contains wood flour and a thermoplastic resin as main components and contains 1 to 5 wt% of alkane having a molecular weight of 300 to 1000 g/mol.

That is, when the alkane is added to melt-knead the mixture in the barrel 13 of the extruder 12, the mixture and dissolution of the foaming gas into the thermoplastic resin can be promoted, and the foaming gas can be prevented from entering the wood powder, whereby the foaming gas can be uniformly dispersed in the molded material.

The addition of the alkane can reduce the contact resistance between the metal surface and the molded material, and can smoothly move the molded material in which the foaming gas is dispersed in a uniform state, and introduce the molded material 25a into the molding die 30 while maintaining the state in which the foaming gas is dispersed in a uniform state.

Further, by adding the alkane, the expansion of the foaming gas introduced into the thermoplastic resin can be suppressed from starting before the pressure of the molding material 25a is released, and the molding material 25a can be prevented from starting to foam in advance before being introduced into the molding die 30.

As a result, by extrusion foam molding using the molding material, the generation state of internal bubbles is uniform, a high-quality woody foam molded body can be obtained, and the productivity at the time of extrusion molding can be improved.

In the case where the molding material is a granular material obtained by melting and kneading components to form a uniformly dispersed state and then producing the granular material into granules having a predetermined particle diameter, the molding material can be easily used, and the pollution of the working environment can be reduced as compared with the case where the components including powder and the like are used individually.

Further, since the respective constituent components other than the blowing agent are melt-kneaded in advance into a uniformly dispersed state, a uniform melt-kneaded state in which the respective components are not uneven can be more easily obtained when melt-kneaded in the extruder 12.

In addition, the ratio of the wood powder to the thermoplastic resin is as follows: when the wood powder is 50 to 55 wt% and the resin is 45 to 50 wt%, the effect of adding the alkane can be reliably obtained.

In addition, by previously containing a filler, a toughening agent, and a pigment in the molding material, particularly by previously forming these raw materials into pellets by melt-kneading, it becomes easier to make the dispersed state of each component uniform when melt-kneading by the extruder 12 or the like.

In the method for producing a wooden molded foam using the molding material, by applying resistance to the molding material 25a at the outlet 13a portion of the extruder 12, the pressure of the molding material 25a in the extruder 12 is increased, and the flow path area of the extrusion die 20 is reduced from the inlet 20a side to the outlet 20b side of the extrusion die 20, so that the effect of preventing the foaming in advance by adding the alkane which suppresses the foaming of the molding material 25a in a pressurized state can be exhibited to the maximum extent in the case where the molding material 25a flowing in the extrusion die 20 is maintained in a pressurized state.

As a result, the foaming gas in the extruder 12 and the extrusion die 20 can be uniformly dispersed, and the extrusion amount (weight) of the molded material 25a can be increased, thereby improving productivity.

Further, the apparatus for producing a woody molded foam, in which the perforated plate 22 is provided in the outlet 13a portion of the extruder 12 and the resistance 26 is provided in the extrusion die 20, can reliably raise the pressure of the molding material 25a in the barrel 13 of the extruder 12 and maintain the pressure in the extrusion die 20, thereby maximizing the effect of improving the dispersibility of the foaming gas and preventing the paraffin addition in advance such as foaming.

In particular, the outlet of the extrusion die and the inlet of the forming chamber of the forming die are made to have the same shape, the end (mandrel part 26c) of the resistance material 26 on the side of the forming die 30 is formed in a shape similar to the shape of the outlet 20b of the extrusion die 20, and the end (mandrel part 26c) of the resistance material 26 on the side of the forming die 30 is formed in a shape slightly smaller than the shape of the outlet 20b of the extrusion die 20, and the end portion (mandrel portion 26c) of the resistance material 26 on the side of the molding die 30 is disposed at the center in the outlet 20b of the extrusion die 20, when the formed material 25b passes through the narrow space formed between the two, the distribution of the foaming gas in the formed material 25b can be made more uniform, a synergistic effect with the action of the alkane can be obtained, so that the distribution of bubbles in the resulting wood foam molding can be made more uniform.

Further, the extrusion molding apparatus 11 for a woody foamed molded article using a twin-screw extruder as the screw extruder 12 can achieve an effect of further accelerating the mixing and dissolution of the foaming gas in the thermoplastic resin by the addition of the alkane while making the dispersion state of each component more uniform with the melt kneading of the molding material in the extruder 12.

Drawings

FIG. 1 is an explanatory view of a pellet production apparatus used for producing the molding material of the present invention.

FIG. 2 is an explanatory view of an extrusion molding apparatus used for extrusion foam molding of the molding material of the present invention.

Fig. 3 (a) is a longitudinal sectional view of the extrusion die, and fig. 3 (B) is a transverse sectional view.

Fig. 4 (a) is a front view of the porous plate, and fig. 4 (B) is a sectional view taken along line B-B in fig. 4 (a).

Fig. 5 (a) is a plan view of the resistance member, fig. 5 (B) is a side view of the resistance member, and fig. 5 (C) is a front view of the resistance member.

Fig. 6 (a) is a longitudinal sectional view of a forming die (first forming die), and fig. 6 (B) is a transverse sectional view of the forming die.

Fig. 7 is an explanatory view of a bending strength test method.

Fig. 8 is an explanatory view of a conventional extrusion molding apparatus.

Fig. 9 is an explanatory view of the state of occurrence of voids and warpage in the wood foam molded body.

Fig. 10 is an explanatory view of an extrusion molding apparatus provided with a perforated plate.

Description of the reference numerals

11 extrusion molding apparatus

12 (screw) extruder

13 canister

13a outlet (of the cartridge 13)

13b charging port (of the barrel 13)

131 melting zone

132 blowing agent decomposition zone

133 foaming gas mixing zone

14 quantitative supply device

14a molding material feeder

14b blowing agent feeder

15 screw (of extruder 12)

151 melt-kneading part

152 decomposition promoting part

153 dispersion promoting part

16 jointer

16a mounting hole

17 fixed ring

20 extrusion die

20a inlet (of extrusion die 20)

20b outlet (of extrusion die 20)

Flow path 21 (of extrusion die 20)

22 porous plate

22a small hole

25a formed blank

26 resistance element

26a torpedo shaped part

26b bridge part

26c mandrel part

26d Rib

26e end face

30 forming die

30a inlet (of forming die 30)

30b outlet (of forming die 30)

31 forming chamber

32 flow path of cooling medium

40 granular material manufacturing device

41 quantitative supply device

42 extruder

42a cartridge

43 die nozzle

44 cutting machine

44a cutter

45 centrifugal separator

47 drier

50 pulling machine (leading and taking)

625a formed blank

641 extrusion molding apparatus

642 extruder

643 cartridge

643a outlet (of the cartridge 643)

644 hopper

645 screw

650 mould

650a forming chamber

652 perforated plate

G (internal) voids

X pressure measurement position

Detailed Description

Molding material for extrusion foam molding

The molding material for extrusion foam molding of the present invention is used as a material for molding a plate-like wooden molded body in a foamed state (wooden foam molded body) by extrusion molding, for example, by adding a foaming agent at the time of extrusion molding, and it becomes possible to manufacture a wooden foam molded body having a uniform texture by an extrusion molding apparatus, which has been considered impossible or difficult to realize in the past.

The molding material for extrusion foam molding (hereinafter, simply referred to as "molding material") is obtained by adding 1 to 5 wt% of alkane (C) to wood powder and thermoplastic resin as main components, based on the total amount of the molding material_nH_2n+2) Alkane (C)_nH_2n+2) The molecular weight of (A) is 300 to 1000g/mol, preferably 350 to 800g/mol, and more preferably 400 to 600 g/mol.

In addition to the wood flour, the thermoplastic resin and the alkane, a filler such as talc powder, a pigment for coloring, a toughening agent and other auxiliary materials may be added to the molding material.

Thermoplastic resin

As the thermoplastic resin which is one of the main components of the molding material, various thermoplastic resins such as polypropylene (PP), Polyethylene (PE), ABS resin, polyvinyl chloride, and the like can be used.

In addition, the thermoplastic resin can be used alone, or a plurality of kinds of thermoplastic resins can be mixed, for example, waste plastic or the like recovered in a state where a plurality of kinds of thermoplastic resins are mixed can be used as a raw material, and polypropylene (PP) among the thermoplastic resins is used in the present embodiment.

The polypropylene (PP) may be a homopolymer, a random copolymer, a block copolymer, or the like, and any of the polypropylenes described in the present invention may be used, and for example, a polypropylene container recovered by a container reuse method (so-called "compatibilization method (compatibilization リ method)") or various containers mixed with polypropylene may be used.

The thermoplastic resin used in the present invention is preferably a thermoplastic resin having an MFR (melt flow rate) in the range of 0.5 to 10(g/10 min), and for example, a resin having an MFR in the above-mentioned numerical range can be obtained by mixing a plurality of thermoplastic resins having different MFR.

Wood flour

Wood flour, which is another main component of the molding material, may be obtained by crushing waste materials such as virgin wood, used construction waste, sawdust generated during wood processing, and the like, using a crusher, a cutter, a pulverizer, and the like, in addition to various wood flours generally commercially available.

The wood species to be used is not particularly limited, and there is no problem in structure even if a plurality of kinds of wood are mixed, but it is preferable to use wood having a color tone close to a certain degree in consideration of the completion of the finally obtained woody molded foam.

The wood powder used may have a particle size of 1000 μm or less, and it is preferable to use wood powder having a particle size of 150 to 200. mu.m.

From the viewpoint of improving the fusibility with the thermoplastic resin and preventing generation of water vapor during heating and kneading, it is preferable to over-dry the wood flour before mixing with other raw materials, and it is preferable to use wood flour dried to a water content of 1 wt% or less.

The ratio of the wood powder to the thermoplastic resin is preferably 50-55 wt%/45-50 wt%.

Alkane(s)

In the present invention, alkane (C) is added to the molding material_nH_2n+2) Various alkanes (C) having a molecular weight of 300 to 1000g/mol can be used_nH_2n+2). Since alkanes having a molecular weight of less than 300g/mol have low melting and boiling points, they are difficult to use, and on the other hand, they can be confirmed from the test results described below: when an alkane having a molecular weight of more than 1000g/mol is used, the desired effect cannot be obtained. In other words, when the lower limit is 300g/mol or less, the boiling point is low (50 ℃ or less) because of the fluid approximation, and the lower limit isAt 300g/mol or more, the wax becomes a petroleum wax (solid). When the resin (PP) is fluid, the resin (PP) becomes less dispersible and precipitates on the surface, and the desired effect cannot be obtained.

Further, the molecular weight of the alkane to be added is preferably in the range of 350 to 800g/mol, more preferably 400 to 600 g/mol.

The amount of the alkane added is 1 to 5 wt% based on the whole molding material. If the amount is less than 1 wt%, no effect is obtained, and if the amount is more than 5 wt%, paraffin comes off to the surface, resulting in a decrease in expansion ratio.

Other additive materials

The molding material may contain, in addition to the wood powder, the thermoplastic resin and the alkane, a filler such as talc in an amount of about 5 to 30 wt% based on the entire molding material, a coloring pigment, a toughening agent, and the like.

The talc powder, which is exemplified as the filler, is added to improve the strength of the finally obtained wood composite board, and may be added in an amount of 5 to 25 wt% based on the total weight of the molding material, and if the amount of talc powder added is small relative to the amount of the talc powder added, the strength cannot be improved, whereas if the amount of talc powder added is too large, the finally obtained wood composite board becomes brittle and the strength is rather lowered.

The particle size of the talc to be added may be in a relatively wide range, and it is preferable to use talc having an average particle size of about 5 to 30 μm.

The pigment is added for coloring the finally obtained wood composite board, and the pigment is added in various proportions corresponding to the color to be obtained in the final product.

For example, in the present embodiment, a silver oxide pigment is used for coloring brown, and the pigment is added in an amount of about 3 wt% based on the entire molding material.

In addition, a toughening agent may be added as an additive, and as described above, in the present embodiment in which polypropylene is used as a thermoplastic resin as a main raw material, maleic acid-modified polypropylene is added as the toughening agent, whereby the bondability between wood flour and the resin can be improved.

If the amount of the toughening agent added is too small, no effect is obtained, while if the amount of the toughening agent added is too large, the effect is increased, but the cost is also increased, and as an example, it is preferable to add the toughening agent in an amount of about 0.3 to 2.0 wt% based on the whole of the molding material to be obtained.

Production of shaped materials

It is preferable that the wood flour, the thermoplastic resin, the alkane, and the optional filler such as talc, the pigment, and the toughening agent constituting the molding material are previously uniformly stirred or the like to form a mixed material, and it is more preferable that the above-mentioned constituting material is previously melt-kneaded while being heated so that each component is uniformly dispersed, and then the kneaded material obtained by melt-kneading is produced into particles having a predetermined particle size to form the molding material into pellets.

The granulation of the molding material with melt kneading as described above can be carried out by a known granulation apparatus such as a granulator or a henschel mixer, and the granular material production apparatus 40 shown in fig. 1 is used in the present embodiment as an example.

The pellet manufacturing apparatus 40 shown in fig. 1 includes: a quantitative supply device 41 for quantitatively supplying each constituent component of the molding material by a weight loss compensation method (ロスインウエイト method) or the like; the screw extruder 42 melts and kneads the raw material quantitatively supplied from the quantitative supply device 41 at a temperature of about 170 to 180 ℃ and extrudes the resulting kneaded product. A die nozzle 43 having a plurality of small holes formed therein is provided at the tip of the barrel 42a of the extruder 42, and the molten material (strand) extruded in a round string shape is extruded into hot water by the die nozzle 43, and cut by a cutter blade 44a of the cutter 44 to a predetermined length, whereby pellets are produced by a hot cutting method in water (underwater).

As the extruder 42, various known extruders can be used, but a twin-screw extruder is preferably used.

The twin-screw extruder has two screws that are engaged and rotated in such a manner that the screw thread and the screw groove are staggered, and in this embodiment, a twin-screw extruder in which the screws are rotated in different directions is used.

The twin-screw extruder has a unique kneading effect by the forced extrusion force and the meshing of the screws by the above-described configuration of the screw meshing, is very effective for the dispersion of the raw material, and can secure a required extrusion force even if the rotation speed is low, and thus can suppress the temperature rise of the material due to friction, so that the temperature of the material can be easily controlled by a heater (not shown) provided at the outer periphery of the extruder barrel, and thus pellets can be well produced.

The pellets of the molding material obtained as described above are dehydrated by a centrifugal separator 45, and the dehydrated pellets are recovered and used as a molding material for a wood molded foam, which will be described later.

Production of woody molded foam

Drying of the Molding materials (pellets)

The molding material for extrusion foam molding obtained as described above is subjected to extrusion foam molding together with a foaming agent to form a wood foam molded body having a predetermined shape.

Before such foam molding, the produced pellets of the molding material are sufficiently dried by using a dryer 47 shown in fig. 2 or the like as needed.

The drying of the pellets is preferably carried out so that the moisture content of the pellets becomes 0.2 wt% or less. The drying method is not particularly limited, and in the present embodiment, the granular material is dried in a thermal dryer at a temperature of 120 ℃ for 2 hours or more to the above-mentioned moisture content, as an example.

Foaming agent

The blowing agent includes a volatile blowing agent which is a gas or a liquid and a decomposable blowing agent, and generally, the volatile blowing agent (gas type) includes CO₂、N₂Any of these blowing agents can be used, and various commercially available blowing agents can be used. In the present embodiment, a decomposable blowing agent is used.

The decomposable blowing agent includes inorganic compounds, azo compounds, sulfonyl hydrazide compounds, nitroso compounds, azide compounds and the like, and any blowing agent may be used as long as it can be easily dispersed or dissolved in a thermoplastic resin which is a main raw material of a molding material and does not impart unnecessary coloration to the obtained woody foam molded product.

Further, a granular foaming agent called "master batch" in which a foaming agent is added to a carrier resin at a high concentration is also commercially available, and such a foaming agent may be used.

In the present embodiment, a master batch is used in which PE is used as a carrier resin and sodium bicarbonate, which is an inorganic compound, is added as a foaming agent.

The blowing agent is added in a required amount according to the amount of gas generated by the blowing agent to be used, the degree of foaming of the foamed molded article to be produced, and the like, and in the present embodiment, the total amount of the molding material and the blowing agent is 100 wt%, and the amount of the blowing agent (master batch) to be added is preferably 0.3 to 3 wt%, for example.

Thereafter, the molding material to which the foaming agent is added as described above is continuously introduced into the screw extruder 12 provided in the extrusion molding apparatus 11, melt-kneaded while being heated, and the molded material 25a extruded from the extruder 12 is introduced into the extrusion die 20, and then introduced into the molding die 30 following the extrusion die 20, and is molded into a predetermined shape and cooled and solidified, thereby obtaining a wood foam molded body having a desired shape.

Extrusion molding apparatus

Various extrusion molding apparatuses can be used as the extrusion molding apparatus for producing the wooden foamed molded article, and for example, a known extrusion molding apparatus described with reference to fig. 8 or an extrusion molding apparatus modified as described with reference to fig. 10 can be used.

However, in order to maximize the effect of improving the dispersibility of the foaming gas by adding the alkane and preventing the foaming before introduction into the forming die 30, it is preferable to use the extrusion molding apparatus 11, and the extrusion molding apparatus 11 is configured to increase the pressure of the molded material 25a in the extruder 12, introduce the molded material 25a into the forming die 30 while maintaining the pressure of the molded material 25a introduced from the extruder 12 into the forming die 30, and rapidly release the pressure of the molded material 25a in the forming die 30.

An example of the structure of an extrusion molding apparatus 11 suitable for extrusion molding using the molding material of the present invention will be described with reference to fig. 2 to 6.

The extrusion molding apparatus 11 shown in fig. 2 includes: a constant-volume feeder 14 for supplying a granular material of the molding material and a master batch of the foaming agent, which are obtained in the above-described step, in constant volumes; a screw extruder 12 for melting and kneading the pellets of the molding material supplied from the metering device 14 together with a foaming agent and extruding the mixture; an extrusion die 20 into which the extruded material 25a extruded by the extruder 12 is introduced; a forming die 30 for forming the formed material 25a having passed through the extrusion die 20 into a predetermined shape and cooling and solidifying the formed material; and a drawing machine 50 for drawing the extruded material (wooden foam molding) which has passed through the molding die 30 and cooled and solidified.

Quantitative supply device

The dosing device 14 is provided with: a molding material feeder 14a for supplying the pellet of the molding material of the present invention obtained as described above to the extruder 12 in a fixed amount at a time; and a foaming agent feeder 14b for quantitatively feeding the foaming agent as the master batch of the present embodiment and the molding material fed to the extruder 12 by the molding material feeder 14a, respectively, and feeding the molding material and the foaming agent into hoppers provided in the molding material feeder 14a and the foaming agent feeder 14b, respectively, and rotating the feed screw by a motor M provided at a lower portion of the hopper, thereby feeding the granular material of the molding material and the foaming agent to the extruder 12 in a predetermined ratio.

Extruding machine

The extruder 12 into which the molding material and the foaming agent are charged as described above is a screw extruder 12, and the screw extruder 12 has a screw 15, and the screw 15 heats and kneads the mixture of the particulate molding material and the foaming agent to melt and plasticize the mixture, and extrudes the melt-plasticized molding material 25 a. In the present embodiment, an example in which the twin-shaft screw extruder 12 is used as the extrusion molding apparatus 11 is described, but various screw extruders such as a single-shaft type, a multi-shaft type, and a screw extruder combining these can be used.

However, as described above, the twin-screw extruder has a forced extrusion force due to the structure in which the screws 15 mesh with each other and a unique kneading effect, is very advantageous for dispersion of raw materials, and can secure a required extrusion force even at a low rotation speed, and therefore, there are advantages in that the material temperature can be easily controlled by a heater (not shown) or the like provided on the outer periphery of the barrel 13 of the extruder 12 because the material temperature can be suppressed from being increased by friction, and therefore, it is preferable to use a twin-screw extruder as the extruder 12 of the extrusion molding apparatus 11.

The twin-shaft type screw extruder 12 shown in fig. 2 includes: a barrel 13; a pair of screws 15 rotatably provided in the barrel 13; the speed reducer drives the screw rod 15 to rotate; and a driving source M configured by a motor or the like, and provided with an extrusion die 20 and a molding die 30 (described later) on the front end side (front side in the extrusion direction, right side in the drawing sheet in fig. 2) of the barrel 13.

The tube 13 is cylindrical, and the tube 13 has an outlet 13a formed at the front end in the extrusion direction, a closed rear end (the rear end in the extrusion direction, left side in fig. 2), and a raw material inlet 13b formed at the upper part of the rear end and penetrating the inside and outside of the tube 13, and a mixture of a molding material and a foaming agent is charged through the charging port 13b by the above-mentioned constant-volume supply device 14.

A heating member (not shown) such as a band heater is provided on the outer periphery of the drum 13, and is provided so as to be wound around the drum 13 along the entire length of the drum 13 or so as to surround the drum 13 in an outer ring manner, and the mixed material supplied into the drum 13 is heated by the heating member.

The entire length of the cylinder 13 is divided into a plurality of zones (for example, a melting zone 131, a decomposition zone 132 of a foaming agent, and a mixing zone 133 of a foaming gas), and the temperature of each zone 131 to 133 can be independently controlled by a heating means.

The screws 15 are respectively constituted by a rotating shaft of a round bar shape and a thread integrally provided in a spiral manner around the rotating shaft, the thread constituting a thread portion of the screw 15. The rotating shafts (left side in the paper plane in fig. 2) provided at the rear ends of the screws 15 project rearward from the rear end of the barrel 13, the projecting portions are connected to a motor M serving as a drive source, inclined threads and thread grooves formed in the screws 15 are engaged and rotated in a symmetrical state by the drive source, and the screws 15 are double-shaft tapered screws formed in a shape tapered toward the front end side.

The portion of the screw 15 located inside the barrel 13 comprises: a melt-kneading unit 151 disposed in the melting zone 131 and melt-kneading the heated raw material; a decomposition promoting portion 152 disposed in the decomposition region 132 of the foaming agent to promote decomposition of the foaming agent; and a dispersion promoting portion 153 arranged in the mixing region 133 of the foaming gas for promoting the dispersion of the foaming gas, wherein the tooth profile of the screw has a shape corresponding to the above function in each portion.

The screw 15 is driven to rotate by the operation of the drive source M, and the mixed material supplied into the barrel 13 by the quantitative supply device 14 is heated and kneaded, and while being pressure-conveyed in the direction of the tip of the screw 15 along the grooves between the flights of the screw 15, the mixed material becomes a molded material 25a in a molten and plasticized state, and the molded material 25a is extruded from the tip side of the screw 15 to the outside of the barrel 13 by an extrusion force applied to the molded material 25 a.

Here, since the wood flour added to the molding material is a porous material, the wood flour has a property of easily absorbing the foaming gas generated by the decomposition of the foaming agent, as compared with the resin material.

On the other hand, if the foaming gas enters the wood powder, the foaming gas does not sufficiently enter the molten resin, and bubbles are less likely to be formed in the resin portion, and the degree of foaming of the finally obtained wood molded foam is reduced.

However, in the case of using the molding material of the present invention to which the alkane of the above-mentioned molecular weight is added in the above-mentioned amount, the alkane has an action of accelerating the mixing and dissolution of the foaming gas generated by the decomposition of the foaming agent into the thermoplastic resin in the foaming gas mixing zone 133, and on the other hand, the alkane has an action of suppressing the intrusion of the foaming gas into the wood flour.

Extrusion die

The extrusion die 20 introduces the molded material 25a extruded from the barrel 13 of the extruder 12 into a molding die 30 described later while maintaining the pressurized state of the molded material 25a, and the extrusion die 20 is detachably attached to the tip end side of the barrel 13 of the extruder 12 by a bolt or the like through the adapter 16.

The extrusion die 20 includes: an inlet 20a having a shape conforming to the shape of the outlet 13a of the barrel 13 of the extruder 12; and an outlet 20B having a shape corresponding to the shape of an inlet 30a of a forming die 30 described later, and as shown in fig. 3a and 3B, the width of the flow path 21 of the extrusion die 20 in the vertical direction in the longitudinal section (see fig. 3a) is a shape that decreases from the inlet 20a side toward the outlet 20B side, and the width of the flow path 21 in the horizontal section (see fig. 3B) gradually increases from the inlet 20a side toward the outlet 20B side, then slightly decreases toward the outlet 20B, and then becomes the same as the width of the inlet 30a of the forming die 30 described later, whereby the outlet 13a of the barrel 13 of the extruder 12 and the inlet 30a of the forming die 30 can be communicated with each other.

A perforated plate 22 is fitted and attached to the adaptor 16 attached to the inlet 20a side of the extrusion die 20, and a resistance 26 is disposed in the flow path 21 of the extrusion die 20, and the resistance 26 applies resistance to the molding material 25a flowing in the flow path 21 and regulates the flow of the molding material 25 a.

As shown in fig. 4 (a) and 4 (B), the porous plate 22 has a disk shape, and a plurality of small holes 22a are formed in the porous plate 22 in a mesh shape.

In order to attach the porous plate 22 to the adaptor 16, the adaptor 16 is provided with an attachment hole 16a extending from the end surface of the adaptor 16 on the extrusion die 20 side toward the extruder 12 side, the attachment hole 16a having a diameter substantially equal to the diameter of the outer periphery of the porous plate 22, and the porous plate 22 is inserted into the attachment hole 16a from the extrusion die 20 side and the fixing ring 17 is further inserted into the attachment hole 16a from the extrusion die 20 side, whereby the porous plate 22 is attached to a predetermined position in the adaptor 16.

Therefore, in the illustrated example, the small holes 22a of the porous plate 22 and the inner periphery of the fixed ring 17 form a part of the flow path of the molding material 25a in the adaptor 16.

In this way, by installing the perforated plate 22 between the outlet 13a of the extruder 12 and the inlet 20a of the extrusion die 20, the molded material 25a extruded from the extruder 12 is introduced into the extrusion die 20 after passing through the small holes 22a formed in the perforated plate 22, and the extruded material 25a to be extruded from the extruder 12 receives resistance when passing through the small holes 22a formed in the perforated plate 22, so that pressure can be applied to the molded material 25a in the barrel 13 of the extruder 12.

The resistance material 26 formed in the flow path 21 of the extrusion die 20 can maintain the molded material 25a in the extrusion die 20 in a pressurized state by applying resistance to the flow of the molded material 25a in the extrusion die 20, and by maintaining such a pressurized state through the extrusion die 20, when the molded material is introduced into the below-described molding die 30, the pressure of the molded material 25a is rapidly released, and the molded material 25a is easily foamed in the outlet 20b portion of the extrusion die 20 (the inlet 30a portion of the molding die 30).

In order to make such pressure relief possible, as shown in fig. 3 (a), 3 (B), and 5 (a) to 5 (C), the resistance member 26 includes: a bridge portion 26b having a body formed in a rectangular parallelepiped shape, the rectangular parallelepiped body being formed by extending an end portion of a blade-shaped torpedo portion 26a having a width and a thickness gradually increasing from the inlet 20a side to the outlet 20b side of the extrusion die 20, and the bridge portion 26b being provided with a rib 26d for fixing at a predetermined position in the extrusion die 20; and a mandrel portion 26c having a thickness and a width that are slightly narrowed from the bridge portion 26b toward the outlet 20b of the extrusion die 20 and then extended to the outlet 20b of the extrusion die 20 with a certain width and thickness.

The rectangle forming the outline of the end face 26e (see fig. 5C) of the mandrel portion 26C on the side of the outlet 20B of the extrusion die 20 is similar to the rectangle drawn on the inner periphery of the outlet 20B of the extrusion die 20, and the rectangle forming the outline of the end face 26e of the mandrel portion 26C on the side of the outlet 20B of the extrusion die 20 is slightly smaller than the rectangle drawn on the inner periphery of the outlet 20B of the extrusion die 20, and by disposing the mandrel portion 26C at the center inside the outlet 20B of the extrusion die 20, the molding material 25a is introduced into the molding die 30 through a relatively narrow gap (see fig. 3a and 3B) formed between the inner wall of the outlet 20B of the extrusion die 20 and the outer periphery of the mandrel portion 26C.

As described above, by disposing the resistance 26 having the torpedo portion 26a, the bridge portion 26b, and the mandrel portion 26c in the extrusion die 20, the molding material 25a passing through the extrusion die 20 becomes a molding material flow along the inner wall of the flow path 21 of the extrusion die 20 due to the resistance 26, and since the molding material flow is relatively thin when passing through the gap between the inner periphery of the outlet 20b of the extrusion die 20 and the outer periphery of the mandrel portion 26c, it contributes to uniform dispersion of the foaming gas in the molding material 25 a.

Further, since the flow passage area in the outlet 20b of the extrusion die 20 formed in the same shape as the inlet 30a of the forming die 30 described later is sufficiently smaller than the area of the inlet 30a of the forming die 30 due to the presence of the mandrel portion 26c, the pressure of the formed material 25a introduced into the forming die 30 through the outlet 20b of the extrusion die 20 is rapidly released, and the foaming gas in the formed material 25a starts to rapidly expand when the pressure is released.

When the molding material passes through the extrusion die 20, the alkane added to the molding material reduces the resistance between the molding material 25a and the inner surface of the flow path of the extrusion die 20, and has an effect of homogenizing the molding material 25a and smoothly moving the molding material 25a, and an effect of maintaining the homogenized state of the molding material 25 a.

As described above, the extrusion die has a function of maintaining a state in which the foaming gas is dissolved in the molding material 25a in a pressurized state, and a function of preventing the foaming gas from starting to expand until the pressure is released by introduction into the molding die 30 described later.

Forming die

As described above, the molding material 25a having passed through the extrusion die 20 is introduced into the molding die 30, formed into a predetermined shape determined by the shape of the molding chamber 31 formed in the molding die 30, and cooled and solidified to be a wood foam molded body.

As shown in fig. 2, in the present embodiment, the molding die 30 is formed by an aggregate of a plurality of dies, an inlet 30a of the first molding die 301 communicates with an outlet 20B of the extrusion die 20 (see fig. 6a and 6B), a second molding die 302 is disposed at a predetermined interval on the outlet side of the first molding die 301, a third molding die 303 is disposed at a predetermined interval on the outlet side of the second molding die 302, and in the illustrated embodiment, the molding die is continuously disposed to a seventh molding die 307 (see fig. 2).

The molding chambers 31 having cross-sectional shapes corresponding to the shapes of the outlets 20b of the extrusion dies 20 are formed in the respective molding dies 301 to 307, and in the present embodiment, flow passages 32 for a cooling medium are provided in the walls of the first to third molding dies 301 to 303, and the temperature of the extruded material 25a is gradually lowered and solidified by introducing the cooling medium such as cooling water into the flow passages 32 for the cooling medium, thereby obtaining a desired foamed molded body.

In the present embodiment, no flow path for the cooling medium is provided in the walls of the fourth to seventh forming dies 304 to 307.

When the molding material 25a introduced from the extrusion die 20 is introduced into the first molding die 301 of the molding die 20 formed as described above, the molding material 25a extruded into the first molding die 301 is rapidly released from pressure according to the above-described configuration of the extrusion die 20, and the foaming gas generated from the foaming agent decomposed at the time of melt kneading in the extruder 12 is rapidly expanded at the position, thereby foaming the molding material 25 a.

The molding material 25a foamed as described above fills the molding chamber 31 in the first molding die 301, is molded into a shape corresponding to the shape of the molding chamber 31, and is cooled and solidified.

The molded material molded and cooled in the first molding die 301 to be a molded product of a wood molded foam is drawn by the drawing machine 50, passed through the first molding die 301, and then cooled while passing through the second molding die 302, the third molding dies 303 and … …, and the seventh molding die 307 in this order, thereby completing the production of the wood molded foam.

The alkane added to the molding material improves the smoothness of the molding material and the molded woody foamed article with respect to the inner wall of the molding chamber 31 of the molding die 30, and has an effect of maintaining the smoothness of the surface of the molded woody foamed article to be produced.

As a result, it is possible to favorably prevent wrinkles and the like from being formed on the surface of the foam molded body due to unstable flow such as pulsation of the molded material 25a caused by foaming.

Examples

The results of comparative tests between examples of production of a woody synthetic foam produced using the molding material of the present invention (examples 1 to 7) and a woody molded foam obtained therefrom, and examples of production using the molding material of comparative examples (comparative examples 1 to 10) and a molded product obtained therefrom are shown below.

Purpose of the experiment

The influence of the addition of alkane and the change in the molecular weight and the amount of addition of alkane on the moldability of the woody molded foam and the physical properties of the obtained woody molded foam was confirmed, and the optimum molecular weight and the optimum amount range of addition of alkane were determined.

Production conditions

Composition of the Molding materials

The ingredients of the molding materials used in the examples and comparative examples are shown in table 1.

TABLE 1 composition Table of molding materials of examples and comparative examples

In addition, in the molding material, the composition of the molding material of comparative example 6 is included in the scope of the molding material of the present invention, but as described later, because the extrusion molding is not performed by adding a foaming agent to the molding materials of comparative examples 6 and 7, it is described as "comparative example".

Comparative examples 8 to 10 added a foaming agent.

In Table 1, wood flour of examples 1 to 5 and comparative examples 1 to 7 is "A-100" (particle size 50 to 200 μm) manufactured by カネキ fuel Limited; the resin is prepared by mixing OG. PP (other outer product PP) (MFR is 1.0) and bottle cap regenerated PP (MFR is 10.0) according to the weight ratio of 1: the obtained block PP (MFR ═ 5) was mixed at a ratio of 1.

The PE used in examples 6 and 7, and comparative examples 9 and 10 was High Density Polyethylene (HDPE) "HY 430" manufactured by japan ポリエチレン (ltd.), and the blending ratio was PP: PE ═ 1: 1, the molecular weight of the alkane alone was different in examples 6 and 7, and the molecular weight and the compounding ratio of the alkane were different in comparative examples 9 and 10.

Talcum powder is "SP-40" (average particle size 23 μm) of Fuji タルク, .

The pigment was "ブラウン 710" (silver oxide series) from Korea Industrial Co., Ltd.

The toughening agent was "ユーメックス 1010" (maleic acid modified PP) available from Sanyo Kabushiki Kaisha.

The blowing agent was "ポリスレン EE 405F" (master batch with sodium bicarbonate added to the carrier resin PE) permanently made available from Hakka corporation.

In addition, examples 1, 3 and 6 used "Mitsui ハイワックス 100P" of Mitsui chemical corporation as alkanes; examples 2, 4, 5 and 7 used "155 ° F ワックス" of japan ceresin wax (ltd.); comparative examples 2 and 9 used "Mitsui ハイワックス 200P" of Mitsui chemical corporation; comparative examples 3 and 7 used the "Mitsui ハイワックス 410P" of Mitsui chemical corporation; comparative example 4 "Mitsui ハイワックス 100P" of Mitsui chemical corporation was used; comparative examples 5, 6, 8 and 10 used "155 ℃ F. ワックス" of Japan wax ("Japan wax").

Preliminary mixing conditions

The raw materials were melted and kneaded by the pellet production apparatus described with reference to fig. 1 to prepare pellets.

The extruder is a biaxial parallel screw (phi 65) rotating in different directions, and melt-kneading is carried out at a temperature of 170 to 180 ℃ in the extruder to extrude strands having a diameter of about 4mm, and the strands are thermally cut into about 6mm pieces in water.

The obtained pellets of the molding material were dehydrated by a centrifugal separator until the water content was 2% or less.

Extrusion foaming molding conditions

The pellets of the molding material obtained by preliminary kneading are extruded by the extrusion molding apparatus described with reference to fig. 2 to 6.

In each of examples 1 to 7 and comparative examples 1 to 5, "ポリスレン EE 405F" (master batch prepared by adding sodium bicarbonate to PE as a carrier resin) which was permanently neutralized, was used as a blowing agent, and 0.5 wt% of the total weight of a molding material and the blowing agent was added, followed by extrusion molding.

In comparative examples 6 and 7, the extrusion molding was performed using only pellets of the molding material without adding a foaming agent.

Comparative examples 8 to 10 added a foaming agent.

The extruder used was a conical twin screw extruder "T-58" made by Cincinnati Extrusion technology corporation (Cincinnati Extrusion) that rotated in different directions.

Before being charged into an extruder, pellets of the molding material obtained by preliminary kneading are dried at 120 ℃ for 2 hours or more with a thermal dryer to a water content of 0.2% or less, and then charged into the extruder together with the above-mentioned foaming agent.

The extrusion temperature (set temperature of the extruder to the extrusion die) was set to 180 to 190 ℃, and the water cooling jacket of the forming die (first to third forming dies) was set to 90 ℃.

Further, in the molding, the degassing port provided in the barrel of the extruder is not evacuated, and the degassing port is opened to the atmosphere.

By doing so, a plate-like wooden molded foam having a width of 145mm and a thickness of 25mm was continuously formed in the longitudinal direction.

Measuring and viewing content

Measurement of changes in the condition of a formed blank

In order to confirm the change in the state of the molded material due to the change in the molecular weight and the amount of the alkane used, the pressure of the molded material was measured at a predetermined position on the inlet side of the extrusion die (the position indicated by the arrow X in fig. 3a), and the extrusion amount per hour of the extrusion molding apparatus when the extruder was driven at the maximum output was measured as the maximum extrusion amount (kg/Hr), that is, the amount when the extruder was operated at a screw rotation speed of 90% of the maximum torque of the motor was measured.

The maximum extrusion amount was set to a target value of 70(kg/Hr), and the case where the maximum extrusion amount equal to or larger than the target value was obtained was evaluated as "O", and the case where the maximum extrusion amount was smaller than the target value was evaluated as "X". Measurement of physical Properties of the molded article (sheet Material) produced

In order to confirm the influence of the change in the molecular weight and the amount of the alkane used on the finally obtained molded article (sheet), the density, weight, flexural strength and surface smoothness of the obtained molded article (sheet) were measured or confirmed, respectively.

The density is 0.80 to 0.85g/cm³Set to a target value at which the density isThe range was evaluated as "O", and the density outside the numerical range was evaluated as "X".

The weight of the plate was measured by cutting the plate material formed to have a width of 145mm and a thickness of 25mm to a length of 2000mm, and the plate weight was evaluated as "o" in the range of 58 to 62kg set as the target value and as "x" outside the numerical range.

As shown in FIG. 7, the bending strength of the plate was measured by cutting the plate material to 500mm in length, placing the plate material on stages arranged at intervals of 400mm, and increasing the load placed on the surface side of the plate material at the intermediate position of the stages, and measuring the load at the time of plate breakage. In this bending strength, 155kg was set as a target value, and a value with a bending strength smaller than the target value was evaluated as "x", and a value with a bending strength equal to or higher than the target value was evaluated as "o".

The observation of the surface properties of the plate material was visually confirmed to confirm whether or not the surface of the plate material had wrinkles due to uneven resin flow, the size of the wrinkles, and the like.

Test results

The results of measurement, observation and evaluation performed with respect to the contents are shown in table 2.

TABLE 2 measurement, observation and evaluation results

Discussion of the related Art

From a discussion of the pressure and maximum extrusion of the formed billet

It can be confirmed that: the pressure of the molded material in the extrusion die of the example of extrusion foam molding using the molding material of examples 1 to 7 was low in comparison with any of comparative examples 1 to 5, 9 and 10 except for comparative examples 6 and 7 in which no blowing agent was added and comparative example 8 in which the alkane ratio was higher than the range of the present invention.

On the other hand, it was confirmed that: in the extrusion foam molding using the molding materials of examples 1 to 7, the maximum extrusion amounts showed high values of 70(kg/Hr) or more, and the maximum extrusion amounts were equal to or more than those of comparative examples 6(75kg/Hr) and 7(65kg/Hr) to which no foaming agent was added.

Example 6 substantially the same evaluation as in example 1 was obtained except for the strength. Example 7 was evaluated in substantially the same manner as in example 2 except for the strength (the same applies to the following discussion, and therefore, the evaluation is omitted).

In comparative example 8, the use of the alkane of the present invention in an amount not less than the amount used in the present invention is not preferable because the foaming rate is lowered to inhibit foaming.

Comparative example 9 substantially the same evaluation as in comparative example 2 was obtained except for the strength. Comparative example 10 was evaluated in substantially the same manner as comparative example 5 except for the strength (the evaluation is also omitted in the following discussion).

From the above points, it can be confirmed that: in the extrusion molding using the molding materials of examples 1 to 7, the addition of the alkane of the predetermined molecular weight of the present invention in the predetermined amount of the present invention has an effect of suppressing the expansion (pre-foaming) of the foaming gas generated by the decomposition of the foaming agent in the cylinder and the extrusion die of the extruder, and has an effect of promoting the expansion of the foaming gas when the pressure is released from the extrusion die.

That is, if the alkane added to the raw material does not exhibit the function of suppressing the advance foaming in the extruder and the extrusion die, the volume of the molded material increases due to the advance foaming, and the pressure in the extrusion die should be increased to the same level as the measurement result (8.0MPa) of comparative example 1 in which no alkane is added.

However, the fact that the pressures in the extrusion die measured in examples 1 to 7 were not only lower than the pressure (8.0MPa) in comparative example 1 but also lower than those in other comparative examples (comparative examples 2 to 5, comparative example 7, comparative example 9, and comparative example 10) means that the addition of the alkane having the predetermined molecular weight of the present invention in the predetermined amount of addition of the present invention can suppress the foaming of the foaming gas in the extruder and the extrusion die in advance.

Further, if the foaming in advance occurs and bubbles are already formed in the molded material in the extruder and the extrusion die, the density of the extruded material passing through the extruder and the extrusion die is reduced. Therefore, if the flow rate of the molded billet (billet volume passing per unit time) passing through the extruder and the extrusion die does not change greatly before and after foaming, the maximum extrusion amount (weight) must be reduced.

However, if the compositions of the comparative molding materials were substantially the same and the comparative examples 1 and 6 were different only in the presence or absence of the addition of the foaming agent, the maximum extrusion amounts of both the comparative examples 1 and 6 were 75(kg/Hr), and no reduction in the maximum extrusion amount was observed even when the extrusion molding was performed with the foaming agent added in the comparative example 1.

Thus, it can be seen that: the density of the molding material in the fluid state in example 1 (the molding material before passing through the extrusion die) was maintained at a density similar to that in comparative example 6, that is, example 1 suppressed the foaming in advance, and the foaming of the molding material rapidly proceeded in a relatively short time after the material exited from the outlet of the extrusion die until the molding material was cooled by the molding die.

It was confirmed that: when the alkane having the molecular weight specified in the present invention is added in the amount specified in the present invention, the pressure maintained in the extruder and the extrusion die and the subsequent release pressure are combined, whereby the foaming in advance in the barrel of the extruder and the extrusion die can be suppressed and the timing of starting the foaming can be controlled.

According to the discussion of physical properties of the foam molded article (sheet material), etc

According to the discussion of density

The foamed molded articles (plate materials) obtained in examples 1 to 7 were low in density and high in expansion ratio, compared with comparative examples 6 and 7 in which no foaming agent was added, and also compared with comparative examples 1 to 5 and 8 to 10 in which the same amount of foaming agent as that in examples 1 to 7 was added.

This makes it possible to understand that: when the alkane having the molecular weight specified in the present invention is added in the amount specified in the present invention, the foaming timing of the molded material can be controlled and the foaming can be accelerated as described above.

Here, it is considered that the main factor of inhibiting foaming is that foaming gas generated by thermal decomposition of the foaming agent enters the wood flour which is the porous substance and therefore does not contribute to foaming in the resin portion, but in the configurations described in examples 1 to 7, it is considered that the addition of alkane does not promote the entry of foaming gas into the wood flour but promotes the entry of foaming gas into the resin portion, and a wood foam molded article having a low density and a high foaming ratio can be produced as compared with the comparative examples.

However, even when alkane having the predetermined molecular weight of the present invention is added, if the addition amount is 0.5 wt%, in comparative examples 4 and 5 which are lower than the lower limit (1 wt%) of the predetermined addition amount of the present invention, it is considered that a low-density and high-foaming-ratio woody foamed molded article cannot be obtained, because if the addition amount of alkane is 1 wt% or less, alkane is mainly absorbed by wood flour and does not contribute to the entry of foaming gas into the resin.

On the other hand, if the amount of alkane added is 1 wt% or more, it is considered that alkane dissolves not only in wood flour but also in the molten resin, whereby the foaming gas is easily taken into the molten resin, and thus foaming at a high expansion ratio as described above can be achieved.

As a result of improving the foamability by adding alkane in examples 1 to 7, the resulting foam-molded article was lighter (see "weight" in Table 2) and the amount of raw material used was reduced.

According to discussion of intensity

The flexural strength of the molded foams obtained using the molding materials of examples 1 to 7 was slightly lower than that of the molded foam of comparative example 1, which is a molded foam obtained by extrusion molding without adding an alkane.

However, the reduction in bending strength due to the addition of alkane is very small, and the value is higher than the above-mentioned standard evaluation value (155 kg of a load of 5kg increased in accordance with JIS a5741 "plastic flat material") which is set as a necessary and sufficient strength in practical use, so that the required strength can be secured.

According to discussion of surface properties

It can be confirmed that: the woody molded foams obtained by extrusion foam molding using the molding materials of examples 1 to 7 were molded in a good surface state without generating large wrinkles on the surface.

In contrast, it was confirmed that: even when the amount of alkane added is within the range specified in the present invention, the surfaces of comparative examples 2, 3 and 9, which have molecular weights exceeding 1000g/mol, have large wrinkles.

Further, it was confirmed that: even when the molecular weight of the alkane used is within the range specified in the present invention, wrinkles are generated on the surface of the woody molded foam obtained in comparative examples 4 and 5, in which the addition amount is less than 1 wt%.

From the above results, it is considered that when the alkane having the predetermined molecular weight of the present invention is added in the predetermined amount of the present invention, the contact resistance between the molding material and the surface of the molding die on the inside of the molding chamber can be reduced, and therefore, the molding material can smoothly move in the molding chamber of the molding die, and as a result, the occurrence of the wrinkles and the like can be favorably prevented. It can thus be confirmed that: the addition of alkane with the molecular weight of 300-1000 g/mol in the addition amount of 1-5 wt% can effectively prevent the generation of the wrinkles.

Further, even in the case of adding an alkane belonging to the above molecular weight range, in example 1 in which 900g/mol of alkane close to 1000g/mol as the upper limit of the molecular weight is added, although there is no problem in practical use, it is confirmed that wrinkles are slightly generated on the surface, and therefore if such wrinkles are to be completely prevented from being generated, it is preferable that the upper limit of the molecular weight of the added alkane is 800g/mol, and it is more preferable that the upper limit of the molecular weight of the added alkane is 600 g/mol.

Others

Uniformity of foamed state

Further, when the cross section of the obtained wooden molded foam was visually observed, in the wooden molded foam obtained using the molding materials of examples 1 to 7, it could not be confirmed that not only the concentration of bubbles and voids occurred in the central portion of the wooden molded foam as described in the conventional art, but also the generation of bubbles was minute and uniform over the entire cross section.

On the other hand, in comparative examples 1 to 5, 9 and 10, although the defect as large as the internal gap G shown in fig. 9, which was described as the conventional technique, was not observed, the generation state of the bubble was not uniform.

From the above results, it can be considered that: even though the wooden molded foams produced using the molding materials of comparative examples 1 to 5, 9 and 10 can prevent the fatal defect of formation of a large void in the central portion by providing the porous plate and the resistance member, the difference is caused by insufficient acceleration of the mixing and dissolution of the foaming gas in the molten resin to uniformize the dispersion state of the foaming gas and insufficient maintenance of such a uniform dispersion state when the paraffin is not added as in comparative example 1 or the molecular weight or the amount of addition of the paraffin is not within the range specified in the present invention as in comparative examples 2 to 5.

It can thus be confirmed that: the addition of 1 to 5 wt% of alkane having a molecular weight of 300 to 1000g/mol is effective for accelerating the mixing and dissolution of the foaming gas in the resin and for uniformly dispersing the foaming gas.

Productivity of production

As described above, in the extrusion molding using the molding materials of examples 1 to 7, the addition of the alkane of the present invention can suppress the foaming of the molding material in advance in the extruder and the extrusion die, and can realize a high maximum extrusion amount, thereby improving the productivity of the woody molded foam.

Here, the production length per hour of the wood molded foam of each example and comparative example obtained by the following formula using the measurement results of table 2 is shown in table 3 below.

[ maximum extrusion amount (kg/Hr)/weight of woody molded foam (kg/2m) ]. times.2000 (mm)

TABLE 3 production Length of Wood-based foamed molded article per hour

	Maximum extrusion volume (kg/Hr)	Formed body weight (kg/2m)	Length of manufacture per hour (m)
				Example 1	75	6.16	24.35
Example 2	75	5.95	25.21
				Example 3	70	6.16	22.73
Example 4	70	6.16	22.73
				Example 5	75	5.95	25.91
Example 6	75	6.16	24.35
				Example 7	75	5.95	25.21
Comparative example 1	60	6.67	17.99
				Comparative example 2	65	6.53	19.91
Comparative example 3	60	6.67	17.99
				Comparative example 4	60	6.67	19.49
Comparative example 5	65	6.53	19.91
				Comparative example 6	75	8.70	17.24
Comparative example 7	65	8.70	14.91
				Comparative example 8	70	6.54	21.41
Comparative example 9	55	6.45	17.05
				Comparative example 10	62	6.53	18.99

From said table 3 it can be determined: in contrast to examples 1 to 7, in which the foamed molded articles (plate materials) of 22.73 to 25.91m per hour were produced, in comparative examples, the minimum value of comparative example 7 (but no foaming) was 14.91mm, and in comparative example, the maximum value of comparative example 8 was 21.41m, and productivity exceeding 22m per hour was not achieved.

This can be confirmed; when the alkane having the molecular weight specified in the present invention is added in the amount specified in the present invention, it is possible to achieve both production of a high-quality woody foamed molded article and improvement in productivity.

Claims

1. A molding material for extrusion foam molding, which is used for producing a wooden foam molded body by adding a foaming agent during extrusion molding,

using wood flour and one or a mixture of polypropylene PP, ABS resin and polyvinyl chloride PVC as main components, or using a mixture of wood flour, polypropylene PP and polyethylene PE as main components, and containing 1-5 wt% of alkane with a molecular weight of 300-1000 g/mol, and making into particles with a specified particle diameter,

the mixture ratio of the wood powder and one or the mixture of the polypropylene PP, the ABS resin and the polyvinyl chloride PVC is as follows: 50-55 wt% of wood flour, 45-50 wt% of one or a mixture of polypropylene PP, ABS resin and polyvinyl chloride PVC, or the mixture ratio of the wood flour to the mixture of the polypropylene PP and the polyethylene PE is as follows: 50-55 wt% of wood powder, 45-50 wt% of a mixture of polypropylene (PP) and Polyethylene (PE),

the water content of the wood powder is less than 1 wt%.

2. The molding material for extrusion foam molding according to claim 1, wherein the molding material for extrusion foam molding is formed into pellets after melt kneading to uniformly disperse the respective components.

3. The molding material for extrusion foam molding according to claim 1 or 2, further comprising a filler and/or a toughening agent and/or a pigment.

4. A method for producing a molding material for extrusion foam molding for producing a wooden foam molded body by adding a foaming agent at the time of extrusion molding,

mixing one or a mixture of wood powder, polypropylene PP, ABS resin and polyvinyl chloride PVC with alkane with the molecular weight of 300-1000 g/mol, wherein the alkane is 1-5 wt% of the whole forming material, or mixing the mixture of the wood powder, the polypropylene PP and the polyethylene PE with the alkane with the molecular weight of 300-1000 g/mol, the alkane is 1-5 wt% of the whole forming material, and the mixture ratio of the wood powder to one or the mixture of the polypropylene PP, the ABS resin and the polyvinyl chloride PVC is as follows: 50-55 wt% of wood flour, 45-50 wt% of one or a mixture of polypropylene PP, ABS resin and polyvinyl chloride PVC, or the mixture ratio of the wood flour to the mixture of the polypropylene PP and the polyethylene PE is as follows: 50-55 wt% of wood flour, 45-50 wt% of a mixture of polypropylene (PP) and Polyethylene (PE), and the water content of the wood flour is less than 1 wt%,

the mixture obtained after the mixing is melt-kneaded into a state in which the respective constituent components are uniformly dispersed, and the obtained kneaded product is produced into granules having a predetermined particle diameter, thereby forming granules.

5. The method of producing a molding material for extrusion foam molding according to claim 4, wherein a filler and/or a toughening agent and/or a pigment is melt-kneaded together with the alkane and one or a mixture of the wood flour, the polypropylene PP, the ABS resin and the polyvinyl chloride PVC, or a mixture of the wood flour, the polypropylene PP and the polyethylene PE and the alkane.

6. A wooden foam molded product obtained by extrusion-molding the molding material according to claim 1 or 2 together with a foaming agent into a predetermined shape by an extrusion molding apparatus.

7. A wooden foam molding obtained by extrusion-molding the molding material according to claim 3 together with a foaming agent into a predetermined shape by an extrusion molding apparatus.

8. A method for producing a wooden foam molded body, characterized in that,

the molding material according to claim 1 or 2, which is introduced into a screw extruder provided in an extrusion molding apparatus together with a blowing agent, and is melt-kneaded at a temperature not lower than the decomposition temperature of the blowing agent,

introducing the molded material extruded from the extruder into a molding chamber of a molding die while maintaining the molded material in a pressurized state,

when the molding material is introduced into the molding chamber of the molding die, the pressure of the molding material is released to foam the molding material, and the molding material is cooled and solidified while being molded into a shape corresponding to the cross-sectional shape of the molding chamber while passing through the molding chamber of the molding die.

9. A method for producing a wooden foam molded body, characterized in that,

the molding material according to claim 3, which is introduced into a screw extruder provided in an extrusion molding apparatus together with a blowing agent, and is melt-kneaded at a temperature not lower than the decomposition temperature of the blowing agent,

10. The method for producing a wooden molded foam according to claim 8, wherein the step of molding the wooden molded foam is performed by molding the wooden molded foam,

an extrusion die is provided between the extruder and the forming die of the extrusion forming apparatus, the extrusion die is communicated between an outlet of the extruder and an inlet of the forming die,

applying resistance to the shaped material introduced into the extrusion die from the outlet of the extruder to increase the pressure of the shaped material in the extruder,

and the flow path area of the extrusion die is reduced from the inlet side to the outlet side of the extrusion die, so that the molded material is introduced into the molding chamber of the molding die while maintaining the pressure of the molded material introduced into the extrusion die from the extruder,

the molded material having passed through the extrusion die is released from pressure when passing through the outlet of the extrusion die, and the molded material is foamed at the inlet portion of the extrusion die.

11. The method for producing a wooden molded foam according to claim 9, wherein the step of molding the wooden molded foam is performed by molding the wooden molded foam,

12. The molding material for extrusion foam molding according to claim 1 or 2, wherein the MFR of one or a mixture of the polypropylene PP, the ABS resin and the polyvinyl chloride PVC, or the mixture of the polypropylene PP and the polyethylene PE is in the range of 0.5 to 10, wherein MFR represents a melt flow rate, and a unit of the MFR is g/10 min.