JPH10100264A - Production of biodegradable foam molded object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate in-mold molding and to enhance mechanical characteristics by bonding a plasticizer of a cellulose derivative to the surfaces of foam particles and thermally plasticizing the surfaces of foam particles to fuse the particles. SOLUTION: Before particles of foam composed of a cellulose derivative are filled into a mold to be thermally shaped, a plasticizer of a cellulose derivative is bonded to the surface of the foam particles in an amt. of 3-30% by wt., pref., 5-15% be wt. of the foam particles. The cellulose derivative constituting the foam particles is obtained by at least apartially esterfying or etherifying hydroxyl groups of cellulose and cellulose acetate into which an acety group is introduced is pref. For example, when the cellulose derivative is cellulose acetate, as the plasticizer, polyethylene glycol and glycerine are used in a mixed state. The plasticizer is bonded to the foam particles by a plasticizer spraying method or a method dripping the plasticizer while the foam particles are stirred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a biodegradable foam molded article. More specifically, a biodegradable foam that can easily form molded articles of various forms such as a heat insulating material, a cushioning material, and a food packaging material, and that has excellent dimensional stability and mechanical properties of the resulting molded article. The present invention relates to a method for producing a molded product.

[0002]

2. Description of the Related Art Conventionally, a wide variety of foams made of synthetic resins have been manufactured and utilized in a wide range of fields such as heat insulating materials, cushioning materials, and food packaging containers. In recent years, the demand for these synthetic resin foams has been increasing year by year, and as a result, the amount discarded has also been increasing year by year, and has been greatly highlighted as an environmental problem and a pollution problem. However, the recycling of waste synthetic resin foam requires a variety of measures on a social scale, while the incineration requires a lot of problems such as prevention of harmful gases and prevention of deterioration of incinerators due to high heat generation. Therefore, development of a foam which can be easily disposed of is strongly desired.

In response to such demands, various foams have been proposed in which these synthetic resins (for example, polystyrene) are replaced with biodegradable resins. For example, JP-A-5-3063
No. 49, JP-A-5-269875, etc.
A method of heating foamed beads or foamed pellets by heating oil-impregnated biodegradable resin chips with oil, then filling this into a mold and heat shaping, and a method of water-impregnated biodegradable resin. Is filled in a mold, and the entire mold is heated with oil to foam, thereby obtaining a foam molded article. However, these methods have a problem that the adhesion between particles is poor and the mechanical properties of the molded product are low. Furthermore, since oil is used as the heating medium, oil tends to remain between the foam particles, and there is a problem that the oil gradually exudes and contaminates.

[0004] In order to improve the adhesion between particles, a method of molding with an adhesive has been proposed. However, many adhesives do not have biodegradability. If the body particles are coated, the biodegradability will be inhibited. Adhesives derived from natural products such as starch and glue, on the other hand, are good in biodegradability, but are easily affected by humidity because they are hydrophilic, and the adhesion is extremely reduced due to moisture absorption and water absorption Therefore, there is a problem that the usage environment is restricted.

[0005] JP-A-5-320405 and JP-A-6-32928 disclose a method for producing foam particles comprising a cellulose derivative such as benzylated cellulose or cellulose acetate. It is also disclosed that the particles are packed in a mold and fused between the foam particles by steam heating to form a molded body. However, when a plasticizer is not blended with the cellulose derivative,
It is difficult to sufficiently fuse the foam particles by steam heating. On the other hand, when a plasticizer is blended with the cellulose derivative, if there is a sufficient amount of the plasticizer for fusing between the foam particles, the entire foam particles are plasticized during the heat fusion treatment. Therefore, the dimensional stability of the molded body obtained by the foam particles being shrunk in reverse is deteriorated, the mechanical properties are also reduced,
Further, there is a problem that the plasticizer is eluted and contaminated when using the molded article. Further, when the amount of the plasticizer is reduced, there is a problem that the plasticization of the cellulose derivative becomes difficult, and the fusion between the foam particles during the molding becomes difficult.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to form various shaped articles such as a heat insulating material, a cushioning material, and a food packaging material. It is an object of the present invention to provide a method capable of easily producing a biodegradable foam molded article having good mechanical properties and easy in-mold molding.

[0007]

According to the study of the present inventors, the object of the present invention is to provide a method for preparing "foam particles comprising a cellulose derivative into a mold and heat shaping the foam particles beforehand. Derivative plasticizer is applied to the surface of foam particles by 3 to 30
% By weight (based on the weight of the foam particles), and the surface of the foam particles is thermoplasticized and fused. Is achieved.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The cellulose derivative constituting the foam particles of the present invention is obtained by at least partially esterifying or etherifying a hydroxyl group in cellulose, and the introduced group includes an acetyl group, a propionyl group, a butyroyl group, and a methyl group. , Ethyl, cyanoethyl, benzyl, octyl and the like. Among them, cellulose acetate having an acetyl group introduced therein is preferred. In this case, the acetic acid esterification degree is an acetylation degree represented by a weight ratio of acetic acid bound to cellulose, which is 45% or more, particularly 47 to 60% (the number of bound acetyl groups per unit of cellulose). Is preferably 1.9 to 2.8).
If the acetylation degree is less than 45%, the melting temperature becomes too high. It is difficult to stably melt-mold the foam particles.

The above-mentioned cellulose derivative may be blended with other substances (excluding plasticizers) as long as the object of the present invention is not impaired, and examples thereof include a heat stabilizer, a foam regulator, and a foaming aid. . Among them, foaming regulators such as inorganic fine particles such as talc, silicon oxide, titanium oxide, magnesium oxide, aluminum oxide and calcium silicate, and organic fine particles such as cellulose powder, chitin, chitosan, wood powder, and metal stearate. Particularly, talc can impart more suitable foaming properties to the cellulose derivative, so that uniform and highly foamed foam particles can be easily obtained. Such foam control agents may be used alone or in combination of two or more. Furthermore, for the purpose of improving foamability, neutralizing acidic substances by-produced during the production of foam particles and generating gas, for example, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, calcium carbonate, etc. Inorganic fine particles may be used in combination.

The amount of these foaming regulators and foaming assistants to be added to the cellulose derivative is suitably in the range of 2 to 50% by weight, preferably 5 to 30% by weight, based on the weight of the cellulose derivative. If the amount is less than 2% by weight, the effect of adding these additives will not appear. For example, if the amount of the foaming regulator is small, uneven and coarse foamed cells are likely to be formed. Is likely to occur, so that non-uniform and coarse foam cells are likely to be formed, and the fraction of the cellulose derivative is reduced, so that the foamability is also reduced.

The foam particles comprising the above-mentioned cellulose derivative used in the present invention have an apparent density of 0.01.
０．１0.12 g / cm ³ , preferably 0.014 to 0.0
It is preferable that the ratio of the major axis to the minor axis (major axis / minor axis) is in the range of 1 to 10, preferably 1 to ³ , 64 g / cm ³ . When the apparent density is less than 0.01 g / cm ³ , the mechanical properties such as the strength of the obtained foam molded article are reduced. Conversely, when the apparent density exceeds 0.12 g / cm ³ , The hardness of the molded product increases, and the properties as a cushioning material, a heat insulating material, and a filler become insufficient. In addition, long axis /
If the short axis ratio exceeds 10, the particles become rods or strings rather than particles, so that it is difficult to uniformly fill the mold, and density irregularities are likely to occur in the obtained molded product. Here, the apparent density is obtained by dividing the weight of the foam particles by the volume of the foam particles, and the long axis / short axis ratio is the length of the longest axis direction and the shortest axis direction of the foam particles. Is the ratio of

The size of the foam particles is preferably such that the diameter of the cut area in the short axis direction is 3 to 20 mm, preferably 5 to 10 mm when converted to a circle. If the amount is less than this range, the foam particles become too small and the handleability deteriorates. On the other hand, if it is too large, a molded product obtained by filling and heat shaping in a mold tends to have a large cavity.

The production of the above-mentioned foam particles is not particularly limited, and may be produced by any method. Taking cellulose acetate as an example, cellulose acetate 10
0 to 100 parts by weight of a cellulose acetate and water as a foaming material are added to 3 to 10 parts by weight of a mixture obtained by adding 2 to 50 parts by weight of a foaming agent, a foaming aid, and the like as needed.
0 parts by weight, preferably 5 to 50 parts by weight, and the mixture is heated to a temperature of 120 to 250 ° C, preferably 1 to 50 parts by weight.
Heat-melt and knead at 80-220 ° C, then diameter 0.5-5
Extrude from a die with a pore size of mm. Melt kneading time is
Since it differs depending on the discharge amount per unit time, the melting and kneading temperature, and the like, it cannot be unconditionally determined, but it is sufficient that the mixing time is sufficient to uniformly melt and knead the mixture.
The die temperature of the discharge section may be the same as the melt-kneading temperature, but may be lower than the temperature within a range where discharge is possible.

The extruder used for melt-kneading may be any type of extruder as long as water is forcibly dissolved in cellulose acetate under high temperature and high pressure. A single-screw or twin-screw extruder is used.

Next, the starting position of foaming (expansion) of the molten cellulose acetate discharged from the die pores differs depending on the temperature and the amount of water, but foaming usually starts from a position 0.1 mm away from the die portion. It is preferable to cut the material in the foaming process. By cutting in the melt plasticized state before the cellulose acetate is solidified in this way, the newly formed cut surface becomes smoother in the process of further expansion after cutting, so the surface is smooth, and Foamed particles are also preferred because rounded corners can be obtained and the filling property in the mold is improved.

The shape of the die pores for extruding the molten cellulose derivative may be any of a circle, a triangle, a square, a rectangle, a star, and a hollow, and may be appropriately selected depending on the purpose.

In the present invention, the plasticizer of the cellulose derivative is added to the surface of the foam particles composed of the above-mentioned cellulose derivative for 3 to 3 days based on the foam particles before filling in a mold and heat shaping. It is important that 30% by weight, preferably 5 to 15% by weight be adhered. By doing so, the bending strength is 0.8 kg / cm ² or more, especially 1.0 kg / cm ^2.
A foam molded article having remarkably excellent properties such as g / cm ² or more is obtained, and the fracture surface of the foam particles is so strongly adhered that the foam cells are broken. When the flexural strength plasticizer adhesion amount is less than 3% by weight, the thermoplasticizing effect on the surface of the foam particles during heat shaping is insufficient, and adhesion unevenness is likely to occur, and the contact area between the foam particles is increased. Is likely to decrease, so that sufficient adhesion cannot be obtained. As a result, the obtained foam molded article is likely to have a problem that the foam particles fall off during use. On the other hand, when the content exceeds 30% by weight, although the adhesiveness between the foam particles is improved, the plasticizer penetrates into the inside of the foam particles, so that the shrinkage of the foam particles at the time of heat shaping becomes large, and the resulting In addition to the deterioration of the dimensional stability and density unevenness of the molded article to be obtained, a problem arises in that the plasticizer is eluted during use and the packaged article is soiled.

In order to attach a plasticizer to the foam particles,
Any conventionally known method may be used, for example, a method of spraying a plasticizer with a spray, a method of dropping a plasticizer while stirring foam particles, and immersing foam particles in a bath liquid filled with a plasticizer. Or a method in which foam particles are pre-filled in a porous mold such as a mesh or punching plate and then dipped in a bath solution filled with a plasticizer. May be selected as appropriate according to the amount of adhesion and the like.

The plasticizer may be applied as it is as a stock solution. Alternatively, the plasticizer may be once diluted with a solvent such as water or alcohol, and then the diluted solution may be applied. By doing so, the viscosity of the adhesion liquid can be reduced, and particularly in a region where the amount of adhesion is small, the uneven adhesion can be suppressed, which is more preferable.
However, if the concentration is too low and the concentration is too low, the amount of liquid to be attached increases and the viscosity also becomes too low, so that the plasticizer easily penetrates into the inside of the foam particles, and the plasticizing temperature between the surface and the inside of the foam particles is increased. , The effect of the present invention is less likely to be exhibited. Therefore, it is desirable that the concentration of the adhesion liquid is appropriately selected depending on the type of the plasticizer to be adhered, the amount of the adhesion, the type of the solvent used, and the like.

The plasticizer used in the present invention is not particularly limited as long as it has a function of plasticizing the cellulose derivative by heating. For example, when the cellulose derivative is cellulose acetate, polyhydric alcohols such as polyethylene glycol, polymethylene glycol, and glycerin;
Phthalates such as dimethyl phthalate, diethyl phthalate, dipropyl phthalate, dipropyl phthalate, dibutyl phthalate, diamine phthalate and dimethoxyethyl phthalate; phosphoric acids such as tributyl phosphate, triphenyl phosphate and tricresyl phosphate Esters: Sebacic esters such as diethyl sebacate, dibutyl sebacate and dioctyl sebacate; Adipates such as dioctyl adipate, butyl butyl octyl adipate and butyl benzyl adipate; tributyl citrate and tri-2-ethylhexyl citrate Citrates such as acetyl tributyl citrate, acetyl trioctyl citrate; and plasticizers such as diisobutyl tartrate, butyl stearate, butyl oleate, soybean oil, castor oil, and camphor. That. These plasticizers may be used alone, or may be used as a mixture of two or more kinds such as polyethylene glycol and glycerin.

The optimum temperature at which the foam particles with the plasticizer adhered are filled into a mold and subjected to thermal shaping varies depending on the type of plasticizer adhered and the amount of the plasticizer adhered, but the temperature is too low. Poor adhesion between the foam particles and
On the other hand, if the temperature is too high, thermal degradation of the plasticizer, coloring, shrinkage of the foam particles, and the like are likely to occur.
It is important to select appropriately according to the type and the amount of the plasticizer in the range of.

Examples of the heat shaping method include a method using a hot press, a method using a heating bath, and a method using a hot air heat treatment machine to blow hot air.

[0023]

The present invention will be described in more detail with reference to the following examples. In addition, each evaluation item in an Example followed the measuring method below. <Adhesiveness (Bending strength, fracture status of fracture surface)> JIS K7
221 standard, width 5cm x height 4cm x effective length 20c
The bending strength of the m specimen was measured using a compression tester manufactured by Intesco. The state of destruction of the fractured surface was visually determined based on the presence or absence of material destruction (destruction of foam cells). Flexural strength exceeds the material strength of the adhesive strength foam particles 0.8 kg / cm ² or more, since the destruction of the foam cells in the fracture surface occurs, the bending strength 0.8 kg / cm ² or more levels was passed . <Shrinkage> The shrinkage was calculated from the size of the obtained molded foam using a plate-shaped mold of 30 cm × 30 cm × 5 cm. When this value was 5% or less, it was regarded as acceptable.

Examples 1-4, Comparative Examples 1 and 2 Foam comprising 90% by weight of cellulose diacetate manufactured by Teijin Limited and 10% by weight of TALC (trade name: LMR-400) manufactured by Fuji Talc Ltd. Particles (major axis / minor axis ratio = 1.5, cut area in the minor axis direction: about 6 mm in diameter in circle) were treated with polyethylene glycol (PEG: average molecular weight 40) as a plasticizer.
0) was applied by a spray gun so as to have a ratio shown in Table 1 with respect to the weight of the foam particles, then filled in a mold, and thermoformed at 150 ° C. for 20 minutes with a hot air drier. The density of each of the obtained foamed molded articles was about 0.045 g / cm ^3.
Met. The adhesiveness and shrinkage of the molded product were as shown in Table 1.

[0025]

[Table 1]

[0026]

The foam particles used in the present invention are environmentally friendly because the material itself has biodegradability and easy incineration, and even if incinerated, there is a problem of toxic gas and incinerator deterioration. Absent. In addition, since a plasticizer is preliminarily attached to the surface of the foam particles, the foam particles can be easily fused to each other when filled in a mold and subjected to thermal shaping, and foaming with excellent mechanical properties can be achieved. A molded body is obtained. Therefore, the foam molded article according to the method of the present invention can be used in various fields by utilizing its features.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Torukei Matsui 3-4-1, Amihara, Ibaraki-shi, Osaka Teijin Limited Osaka Research Center

Claims (3)

[Claims] When filling foam particles made of a cellulose derivative into a mold and performing heat shaping, 3 to 30% by weight (based on the weight of the foam particles) of a plasticizer of the cellulose derivative is previously added to the surface of the foam particles. A method for producing a biodegradable foam molded article, wherein the molded article is adhered, and the surfaces of the foam particles are thermoplasticized and fused. 2. The method for producing a biodegradable foam molded article according to claim 1, wherein the cellulose derivative is cellulose acetate. 3. The foam particles have an apparent density of 0.01 to 0.01.
Method for producing a 0.12 g / cm ^3, the long axis / short axis ratio of 1 to 10 claim 1 or 2 biodegradable foam molded product according.