JP2022010543A - Resin sheet for thermoforming, method for producing the same, and method for producing molding - Google Patents

Abstract

To provide a resin sheet for thermoforming, containing a poly (3-hydroxy butyrate)-based resin, and capable of being molded to a molding having a relatively even thickness by thermoforming.SOLUTION: A resin sheet for thermoforming contains a poly (3-hydroxy butyrate)-based resin. In the resin sheet for thermoforming, a heat shrinkage ratio in an MD direction and/or a TD direction of the resin sheet for thermoforming, measured by heating to 160°C as a temperature indicated by the resin sheet for thermoforming is 2% or more. The resin sheet for thermoforming is obtained by melting with an extruder, a sheet raw material which contains the poly (3-hydroxy butyrate)-based resin followed by molding in a sheet-like shape, and drawing the molded sheet in a uniaxial direction or a biaxial direction at a draw ratio of 1.1 times or more.SELECTED DRAWING: None

Description

The present invention relates to a thermoforming resin sheet containing a poly (3-hydroxybutyrate) resin, a method for producing the same, and a method for producing a molded product from the resin sheet.

In recent years, separate collection and composting of swill have been promoted mainly in Europe, and plastic products that can be composted together with swill are desired. As an example of such a plastic product, Patent Document 1 discloses a processed product obtained by thermoforming a sheet made of a polylactic acid-based polymer.

On the other hand, the environmental problems caused by waste plastics have been highlighted, and it has become clear that a large amount of plastics that have flowed into the sea via ocean dumping or rivers are drifting in the ocean on a global scale. Since such plastics maintain their shape for a long period of time, they have an impact on the ecosystem, such as so-called ghost fishing, which restrains and captures marine organisms, and when ingested by marine organisms, they stay in the digestive tract and cause eating disorders. Has been pointed out.

Furthermore, it has been pointed out that microplastics, which are disintegrated and atomized by ultraviolet rays, adsorb harmful compounds in seawater, and when marine organisms ingest them, harmful substances are taken into the food chain. There is.

The use of biodegradable plastics is expected for marine pollution caused by such plastics, but according to a report compiled by the United Nations Environmental Plan in 2015, the temperature of plastics that can be biodegradable with compost such as polylactic acid is high. It has been pointed out that it cannot be a countermeasure for marine pollution because it cannot be expected to decompose in a short period of time in the low actual ocean.

Under these circumstances, poly (3-hydroxybutyrate) -based resins are attracting attention as materials that solve the above problems because they are materials that can undergo biodegradation even in seawater.

Patent Document 2 describes a polyester resin composition containing two kinds of polyhydroxyalkanoates, and a film or a sheet is mentioned as an example of a molded product thereof, and it is described that a sheet having a thickness of 100 μm is manufactured. ing.

In Patent Document 3, a thermoplastic resin containing polyhydroxyalkanoate as a main component is melted, formed into a film, crystallized, and then rolled at a temperature equal to or lower than the melting point of the resin and higher than the glass transition temperature. It is described that a film is produced by stretching and then secondary stretching at a temperature higher than the rolling temperature.

On the other hand, there is known a method of molding a resin sheet into a container having a recess in the center, such as a food container, by subjecting the resin sheet to thermoforming such as vacuum forming. Although the above-mentioned Patent Document 2 mentions thermoforming, it does not describe that thermoforming was actually performed, and the feasibility of thermoforming is not examined at all. Further, Patent Document 3 does not describe or suggest thermoforming itself.

JP-A-2002-248677 International Publication No. 2015/146194 Japanese Unexamined Patent Publication No. 2006-168159

As a result of the study by the present inventors, when a resin sheet containing a poly (3-hydroxybutyrate) resin is subjected to thermoforming and molded into a molded body such as a container having a deep recess, it is locally formed. It has been found that the strength of the molded product may be insufficient due to the occurrence of a portion having an extremely thin thickness.

In view of the above situation, the present invention provides a thermoforming resin sheet that contains a poly (3-hydroxybutyrate) resin and can be formed into a molded product having a relatively uniform wall thickness by thermoforming. The purpose is to provide.

As a result of diligent studies to solve the above problems, the present inventors have made a resin containing a poly (3-hydroxybutyrate) resin so that the thermoforming rate measured by heating at a specific temperature shows a specific value or more. By constructing the sheet, it was found that the resin sheet can be thermoformed into a molded body having a relatively uniform wall thickness even if it is a molded body such as a container having a shape having a deep recess, and the present invention is completed. I came to do.

That is, the present invention is a thermoforming resin sheet containing a poly (3-hydroxybutyrate) resin, and the thermoforming resin sheet is measured by heating to 160 ° C. as the temperature indicated by the thermoforming resin sheet. The present invention relates to a resin sheet for thermoforming, which has a heat shrinkage rate of 2% or more in the MD direction and / or the TD direction.
Preferably, the poly (3-hydroxybutyrate) resin contains poly (3-hydroxybutyrate-co-3-hydroxyhexanoate).
Preferably, the thermoforming resin sheet further contains a filler, and the content of the filler is 1 to 100 parts by weight with respect to 100 parts by weight of the poly (3-hydroxybutyrate) resin. Preferably, the filler is an inorganic filler, more preferably the inorganic filler is selected from silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, and carbon blacks. Includes at least one species that is Further, preferably, the filler is an organic filler.
Preferably, the difference between the melting point peak temperature in the differential scanning calorimetry of the poly (3-hydroxybutyrate) resin and the end temperature on the high temperature side of the melting point peak is 10 ° C. or higher and 70 ° C. or lower.
Preferably, the thickness of the thermoforming resin sheet is 0.1 to 1 mm.
Preferably, the drawdown of the thermoforming resin sheet measured by the following method is 10 cm or less.
Drawdown: The thermoforming resin sheet of 20 cm in the MD direction x 20 cm in the TD direction on a frame base of 20 cm in length × 20 cm in width × 50 cm in height having a square opening of 17.5 cm in length × 17.5 cm in width in the center. The distance in the vertical direction from the fixed surface of the thermoforming resin sheet to the lowest point when the temperature of the thermoforming resin sheet is heated to 140 ° C.
Further, the present invention is a method for producing the thermoforming resin sheet, which comprises melting a sheet raw material containing the poly (3-hydroxybutyrate) resin with an extruder and then molding the sheet into a sheet. It also relates to a manufacturing method including a step of stretching a molded sheet in a uniaxial direction or a biaxial direction at a stretching ratio of 1.1 times or more to obtain a resin sheet for thermoforming.
Preferably, the temperature of the sheet raw material and the thermoforming resin sheet until the sheet raw material containing the poly (3-hydroxybutyrate) resin is melted by an extruder and then stretched to obtain the thermoforming resin sheet. Is in the range of 40 ° C. or higher and 165 ° C. or lower.
Preferably, the molding into the sheet shape is carried out by sandwiching the molten sheet raw material between two or more rolls.
Preferably, the forming into the sheet shape is carried out by extruding the molten sheet raw material from the T die.
Further, the present invention also relates to a method for producing a molded product, which comprises a step of preheating the thermoforming resin sheet and then molding the resin sheet.
Preferably, the thermoforming resin sheet is preheated to a temperature between the melting point peak temperature in the differential scanning calorimetry of the poly (3-hydroxybutyrate) resin and the end temperature on the high temperature side of the melting point peak.

According to the present invention, there is provided a thermoforming resin sheet that contains a poly (3-hydroxybutyrate) resin and can be formed into a molded product having a relatively uniform wall thickness by thermoforming. Can be done.

The figure which shows the mold used at the time of performing thermoforming in an Example and a comparative example. Top view showing a resin sheet when measuring the heat shrinkage rate in an Example and a comparative example. The figure which shows the frame | frame used when measuring the drawdown in an Example and a comparative example. Side view explaining the drawdown measured in an Example and a comparative example.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

One embodiment of the present invention relates to a thermoforming resin sheet containing a poly (3-hydroxybutyrate) resin.
The poly (3-hydroxybutyrate) -based resin is an aliphatic polyester resin that can be produced from microorganisms, and is a polyester resin having 3-hydroxybutyrate as a repeating unit. The poly (3-hydroxybutyrate) -based resin may be a poly (3-hydroxybutyrate) having only 3-hydroxybutyrate as a repeating unit, or 3-hydroxybutyrate and other hydroxyalkanoates. It may be a copolymer with. Further, the poly (3-hydroxybutyrate) -based resin may be a mixture of a homopolymer and one or more copolymers, or a mixture of two or more copolymers.

Specific examples of the poly (3-hydroxybutyrate) -based resin include poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly (3-hydroxybutyrate). Rate-co-3-hydroxyvariate), poly (3-hydroxybutyrate-co-4-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxyoctanoate), poly (3-hydroxybutyrate), poly (3-hydroxybutyrate) (Hydroxybutyrate-co-3-hydroxyoctadecanoate) and the like can be mentioned. Among them, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly (3-hydroxybutyrate-co-) are easy to produce industrially. 3-Hydroxyvariate) and poly (3-hydroxybutyrate-co-4-hydroxybutyrate) are preferable.

Furthermore, by changing the composition ratio of the repeating unit, the melting point and crystallinity can be changed, and the physical properties such as Young's modulus and heat resistance can be changed, and the physical properties between polypropylene and polyethylene can be imparted. Poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferable from the viewpoint of being possible, industrially easy to produce, and physically useful plastic. In particular, among poly (3-hydroxybutyrate) -based resins having the property of being easily thermally decomposed under heating at 180 ° C. or higher, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) has a low melting point. It is also preferable from the viewpoint that the molding process can be performed at a low temperature.

The composition ratio of the repeating unit of the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) is 3-hydroxybutyrate unit / 3-hydroxyhexanoate unit from the viewpoint of the balance between flexibility and strength. The composition ratio of is preferably 80/20 to 99/1 (mol / mol), and more preferably 75/15 to 97/3 (mo1 / mo1). The reason is that 99/1 or less is preferable from the viewpoint of flexibility, and 80/20 or more is preferable from the viewpoint that the resin has an appropriate hardness.

Examples of commercially available products of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) include Kaneka Corporation "Kaneka Biodegradable Polymer PHBH" (registered trademark).

The melting point, Young's modulus, etc. of the poly (3-hydroxybutyrate-co-3-hydroxyvariate) change depending on the ratio of the 3-hydroxybutyrate component and the 3-hydroxyvalirate component, but both components are co-crystallized. The crystallinity is as high as 50% or more due to the formation, and although it is more flexible than poly (3-hydroxybutyrate), the improvement of brittleness is insufficient.

Generally, in order to mold a resin sheet into a molded body such as a container, thermoforming in which a preheated sheet is molded with a mold is applied. In such thermoforming, the end of the sheet is fixed with a clamp or a pin, the sheet is preheated and softened using a far-infrared heater or the like, and then the sheet is placed along the mold by vacuum or compressed air. To. In such molding, if the preheating is insufficient, the sheet cannot be sufficiently aligned with the mold, resulting in a so-called molded product with poor mold determination. However, if the tension of the softened resin drops too much when preheating is sufficiently performed, the sheet is locally stretched particularly when thermoforming into a molded body such as a container having deep recesses. There is a problem that the strength of the molded product is impaired due to the occurrence of a portion having an extremely thin thickness.

In order to impart excellent thermoformability, the thermoforming resin sheet according to the embodiment of the present invention was heated to 160 ° C. as the temperature indicated by the resin sheet and measured in the MD direction and / or TD of the resin sheet. The thermoforming shrinkage in the direction is 2% or more. The heat shrinkage rate is a numerical value indicating the degree of shrinkage of the resin sheet when the resin sheet is heated. When the heat shrinkage rate is 2% or more, when the resin sheet is softened by heating, the resin sheet shrinks to suppress drawdown, and the resin sheet stretches too much before shaping to make the thickness uneven. It can be prevented from becoming. Therefore, it is possible to form a molded product having a relatively uniform thickness. The thermoforming resin sheet satisfying the heat shrinkage rate can be produced by carrying out a step of stretching at a specific stretching ratio, as will be described later.

Generally, the MD direction is also referred to as a mechanical direction, a flow direction, or a long direction, and the TD direction is a direction perpendicular to the MD direction, and is also referred to as a vertical direction or a width direction. In one embodiment of the present invention, only the heat shrinkage rate in the MD direction may satisfy the numerical range, or only the heat shrinkage rate in the TD direction may satisfy the numerical range. Further, the heat shrinkage rate in each of the MD direction and the TD direction may satisfy the above numerical range.

The heat shrinkage rate is preferably 3% or more, more preferably 5% or more, still more preferably 6% or more. The upper limit of the heat shrinkage rate is not particularly limited, but from the viewpoint of ease of thermoforming, it is preferably 90% or less, more preferably 70% or less, still more preferably 50% or less. It is more preferably 30% or less, and particularly preferably 20% or less.

The heat shrinkage rate is measured as follows. As shown in FIG. 2, the resin sheet is cut into a size of 120 mm in the MD direction × 120 mm in the TD direction, and a square shape of 100 mm in the MD direction × 100 mm in the TD direction is marked in the center thereof. The resin sheet is placed on a paper coated with silica, placed in a dryer set at 160 ° C., heated for 10 minutes, cooled to room temperature, and then on the sides of the square in the MD direction and / or the TD direction. The length is measured, and the heat shrinkage rate is obtained by the formula 1.
Equation 1: Heating shrinkage rate = ((length before heating (mm))-(length after heating (mm))) / (length before heating (mm)) × 100

In one embodiment of the present invention, in order to impart better thermoformability, as a poly (3-hydroxybutyrate) resin, the melting point peak temperature in the differential scanning calorimetry and the end temperature on the high temperature side of the melting point peak are set. It is preferable to use a poly (3-hydroxybutyrate) resin having a difference of 10 ° C. or higher and 70 ° C. or lower. This is because when the temperature difference is 10 ° C. or higher, it becomes easy to melt the poly (3-hydroxybutyrate) resin and at the same time leave some crystals without melting. Thereby, when the sheet is thermoformed, it is possible to realize uniform elongation at the time of molding due to the tension held by the remaining crystals while performing sufficient preheating for molding the sheet. Therefore, thermoforming of the sheet makes it easy to provide a molded body having a relatively uniform thickness.

The temperature difference is more preferably 12 ° C. or higher, further preferably 15 ° C. or higher, and even more preferably 18 ° C. or higher. The upper limit of the temperature difference is 70 ° C. or lower, preferably 50 ° C. or lower, more preferably 40 ° C. or lower, from the viewpoint of ease of manufacturing a poly (3-hydroxybutyrate) resin. It is more preferably 35 ° C. or lower, and even more preferably 30 ° C. or lower.

The melting point peak temperature and the end temperature on the high temperature side of the melting point peak in the differential scanning calorimetry are measured as follows. Obtained when 4 to 10 mg of the resin sample is filled in an aluminum pan and the temperature is raised from 30 ° C. to 180 ° C. at a rate of 10 ° C./min under a nitrogen stream using a differential scanning calorie analyzer to melt the resin sample. In the heat absorption curve, the temperature at which the amount of heat absorption is maximized is defined as the melting point peak temperature, and the temperature at which the melting point peak ends on the higher temperature side than the melting point peak temperature and heat absorption is no longer recognized is defined as the end temperature on the high temperature side of the melting point peak. did. The melting point peak temperature and the ending temperature on the high temperature side of the melting point peak are measured for the entire poly (3-hydroxybutyrate) -based resin contained in the thermoforming resin sheet.

As a poly (3-hydroxybutyrate) resin having a temperature difference of 10 ° C. or more between the melting point peak temperature and the end temperature on the high temperature side of the melting point peak, the poly (3-hydroxybutyrate) resin having a broad melting point peak and containing a high melting point component Butyrate) -based resin can be used. Further, a poly (3-hydroxybutyrate) resin having a broad melting point peak and containing a high melting point component is used in combination with another poly (3-hydroxybutyrate) resin having a different melting point characteristic from the resin. You can also do it.

A specific method for producing a poly (3-hydroxybutyrate) resin having a broad melting point peak and containing a high melting point component is described in, for example, International Publication No. 2015/146194.

The thermoforming resin sheet according to the embodiment of the present invention may not contain a filler, but preferably contains a filler. By including the filler, it is expected to suppress the dimensional change after thermoforming. The filler may be either an inorganic filler or an organic filler, and both may be used in combination. The inorganic filler is not particularly limited, and examples thereof include silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, and carbon black. Only one type of inorganic filler may be used, or two or more types may be used in combination.

The content of the filler is preferably 1 to 100 parts by weight, more preferably 3 to 80 parts by weight, and 5 to 70 parts by weight with respect to 100 parts by weight of the poly (3-hydroxybutyrate) resin. It is more preferably parts by weight, and even more preferably 10 to 60 parts by weight.

The thermoforming resin sheet according to the embodiment of the present invention may contain a resin other than the poly (3-hydroxybutyrate) resin as long as the effect of the present invention is not impaired. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, polybutylene adipate terephthalate, polybutylene succinate terephthalate, and polybutylene aze. Examples thereof include aliphatic aromatic polyester-based resins such as rate terephthalate. As the other resin, only one kind may be contained, or two or more kinds may be contained.

The content of the other resin is not particularly limited, but is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, and 10 parts by weight or less with respect to 100 parts by weight of the poly (3-hydroxybutyrate) resin. Is even more preferable. The lower limit of the content of the other resin is not particularly limited and may be 0 parts by weight or more.

Further, the thermoforming resin sheet according to the embodiment of the present invention preferably does not contain an additive that bleeds out when the resin sheet is stored at 80 ° C. or higher. It has been found in International Publication No. 2015/052876 that the sample to which pentaerythritol is added does not bleed out after being stored at 23 ° C. and a humidity of 50% or less for 1 month, but it bleeds under the storage conditions of 80 ° C. or higher. May be out. Therefore, it is preferable that the thermoforming resin sheet according to the embodiment of the present invention does not contain pentaerythritol. Further, even if a crystal nucleating agent such as pentaerythritol is not contained, a resin sheet for thermoforming can be produced with good productivity by adopting the production method described later.

Further, the thermoforming resin sheet according to the embodiment of the present invention may contain an additive that can be used together with the poly (3-hydroxybutyrate) resin as long as the effect of the present invention is not impaired. Such additives include pigments, colorants such as dyes, odor absorbers such as activated charcoal and zeolite, fragrances such as vanillin and dextrin, plasticizers, antioxidants, antioxidants, weather resistance improvers, and ultraviolet absorbers. , Crystal nucleating agent, lubricant, mold release agent, water repellent agent, antibacterial agent, slidability improving agent and the like. As the additive, only one kind may be contained, or two or more kinds may be contained. The content of these additives can be appropriately set by those skilled in the art according to the purpose of use.

The thickness of the resin sheet for thermoforming according to the embodiment of the present invention is from the viewpoint that uniform preheating can be easily performed in thermoforming, a relatively uniform wall thickness can be produced, and a molded product having a good appearance can be manufactured. From the viewpoint of rigidity and lightness of the obtained molded product, it is preferably 0.1 to 1 mm. If the thickness of the sheet is thinner than the above range, the molded body obtained by thermoforming the sheet will have poor appearance such as wrinkles and surface roughness, and if it is thicker, sufficient preheating will be performed to the extent that it can be shaped. At the same time, it becomes difficult to obtain a molded product having a relatively uniform wall thickness and a good appearance. The thickness of the sheet is preferably 0.15 to 0.8 mm, more preferably 0.20 to 0.6 mm.

The thermoforming resin sheet according to the embodiment of the present invention preferably has a drawdown of 10 cm or less as measured by the following method. The drawdown is a numerical value indicating the degree of the hanging down when the heated and softened resin sheet hangs down by its own weight. When the drawdown is 10 cm or less, it is possible to prevent the resin sheet from being overstretched and having a non-uniform thickness from the time it is softened to the time it is shaped when the resin sheet is thermoformed. Therefore, it is possible to form a molded product having a relatively uniform thickness. The thermoforming resin sheet satisfying the drawdown can be manufactured by carrying out a step of stretching at a specific stretching ratio, as will be described later.

The drawdown is more preferably 9 cm or less, and even more preferably 8 cm or less. The lower limit of the drawdown is not particularly limited, but from the viewpoint of ease of thermoforming, 1 cm or more is preferable, 2 cm or more is more preferable, 3 cm or more is further preferable, and 4 cm or more is particularly preferable.

The drawdown is measured as follows. A thermoforming resin sheet of 20 cm in the MD direction x 20 cm in the TD direction is fixed on a frame base of 20 cm in length × 20 cm in width × 50 cm in height having a square opening of 17.5 cm in length × 17.5 cm in width in the center. The vertical distance from the fixed surface of the thermoforming resin sheet to the lowest point when the temperature of the thermoforming resin sheet is heated to 140 ° C. is defined as drawdown. The lowest point refers to the lowest point when the resin sheet hangs down through the opening under its own weight as shown in FIG. 4 due to softening by heating.

(Manufacturing method of resin sheet for thermoforming)
Next, a method for producing a thermoforming resin sheet according to an embodiment of the present invention will be described.

The method for producing the thermoforming resin sheet according to the embodiment of the present invention is not particularly limited, but the production method is performed after the sheet raw material containing the poly (3-hydroxybutyrate) resin is melted by an extruder. , The process of forming into a sheet, and the formed sheet is stretched in a uniaxial direction (MD direction or TD direction) or a biaxial direction (MD direction and TD direction) at a stretching ratio of 1.1 times or more, and then thermoformed. Includes a step of obtaining a resin sheet for use.

Specifically, the molding into the sheet shape may be carried out by sandwiching the molten sheet raw material between two or more rolls, that is, by a calendar method, or extruding the molten sheet raw material from the T die. That is, it may be carried out by an extrusion molding method. After forming into a sheet, the sheet may be cooled on one or more cooling rolls, or may be cooled by sandwiching it between two cooling rolls.

In general, poly (3-hydroxybutyrate) -based resins have an extremely slow crystallization rate as compared with other crystalline resins such as polypropylene. Therefore, the crystals do not sufficiently solidify on the surface of the cooling roll and tend to easily adhere to the cooling roll. Therefore, the temperature control of the cooling roll is preferably 40 to 100 ° C. for the purpose of promoting crystallization of the poly (3-hydroxybutyrate) resin to some extent and avoiding adhesion to the cooling roll.

In the process of cooling the sheet, the sheet is pulled in the MD direction by making a difference in the rotation speed between the rolls, and / or by clamping the widthwise end of the sheet and pulling it in the TD direction, the sheet is pulled in the MD direction. And / or it is preferable to carry out a step of stretching in the TD direction. By carrying out the stretching step, when the obtained resin sheet for thermoforming is heated, the stretched molecular chains shrink and the entire sheet shrinks significantly. Therefore, the above-mentioned numerical range of the heating shrinkage rate It is possible to obtain a thermoforming resin sheet that satisfies the above requirements.

The stretching ratio in the stretching step is preferably 1.1 times or more, more preferably 1.2 times or more, further preferably 1.3 times or more, and particularly preferably 1.4 times or more. The upper limit of the draw ratio is not particularly limited, but is preferably 3.0 times or less, more preferably 2.5 times or less, still more preferably 2.0 times or less.

It is preferable that the step of forming into a sheet and the step of stretching are continuously performed. Specifically, after performing the step of molding into the sheet shape, a crystallization step (specifically, putting it in ice water for rapid cooling and then annealing at 40 ° C. for 12 hours) is performed as described in Patent Document 3. It is preferable to carry out the stretching step without carrying out the step).

That is, in one embodiment of the present invention, the poly (3-hydroxybutyrate) resin to be applied to the stretching step is not completely crystallized. However, some crystals do not melt and remain in the sheet, and resin crystals and melts are mixed. By carrying out the stretching step on such a sheet, it is possible to obtain a resin sheet for thermoforming that satisfies the above-mentioned numerical range of the heat shrinkage rate, and the above-mentioned complicated crystallization step is not carried out. In both cases, the remaining crystals serve as a starting point during and after the stretching step, and the crystallization of the entire poly (3-hydroxybutyrate) resin is likely to proceed.

From the above viewpoint, the sheet raw material and the thermoforming resin until the sheet raw material containing the poly (3-hydroxybutyrate) resin is melted by an extruder and then stretched to obtain the thermoforming resin sheet. It is preferable to set the manufacturing conditions so that the temperature of the sheet is within the range of 40 ° C. or higher and 165 ° C. or lower. When the temperature exceeds 165 ° C., crystals in the poly (3-hydroxybutyrate) resin cannot remain in the manufacturing process, and as a result, the entire poly (3-hydroxybutyrate) resin is crystallized. May become difficult to progress, and the productivity of the thermoforming resin sheet may decrease. Further, if the temperature is lower than 40 ° C., molding into a sheet or stretching at a predetermined magnification may not be sufficiently performed, and the obtained resin sheet for thermoforming may not satisfy the above-mentioned numerical range of the heat shrinkage rate. There is. The temperature is more preferably 40 ° C. or higher and 165 ° C. or lower, and further preferably 60 ° C. or higher and 160 ° C. or lower.

(Manufacturing method of molded product)
The thermoforming resin sheet according to an embodiment of the present invention is used for molding into a molded body having concave portions and / or convex portions such as a container by thermoforming. As described above, thermoforming can be carried out by preheating and softening the sheet along the mold using vacuum or compressed air. Specific examples of the thermoforming include methods such as vacuum forming, pneumatic forming, vacuum pneumatic forming, matched mold forming, plug assist molding, and TOM forming, but they are simple and the mold cost is low. Vacuum forming and pressure forming are preferable.

The temperature of the sheet achieved by the preheating can be appropriately set by those skilled in the art, but the melting point peak temperature in the differential scanning calorimetry of the poly (3-hydroxybutyrate) resin and the end of the melting point peak on the high temperature side It is preferably a temperature between temperatures. Preheating the sheet to such a temperature melts most of the poly (3-hydroxybutyrate) resin and at the same time leaves some crystals unmelted, which allows shaping. It is possible to achieve both sufficient preheating to a certain degree and uniform elongation due to the remaining crystals, and it is possible to produce a molded product having a relatively uniform thickness.

The device used for preheating the sheet to the above temperature is not particularly limited, and examples thereof include a far-infrared heater, a heat ray heater, and a hot air heater. Far-infrared heaters are preferred. When using a far-infrared heater, the heater temperature is generally set higher than the target seat temperature, and the seat temperature is controlled by the distance between the heater and the seat and the preheating time. For example, a method of installing a far-infrared heater set at 300 to 350 ° C. at a distance of 10 to 50 cm from the seat and heating for 5 to 30 seconds can be mentioned. Examples of the actual temperature of the sheet include a method of measuring with a non-contact thermometer using infrared rays, a method of attaching a thermolabel (registered trademark) whose color changes depending on the temperature to the sheet, and a method of setting preheating conditions.

The molded body obtained by thermoforming the thermoforming resin sheet according to the embodiment of the present invention is not particularly limited, but for example, a container having a recess in the center, a container having a partition, and a folded portion around an opening. Examples include containers, lids, etc.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

In the examples and comparative examples, the following raw materials were used.
(Poly (3-hydroxybutyrate) resin)
A-1: The 3-hydroxyhexanoate (3HH) composition obtained according to the method described in International Publication No. 2013/147139 is 11.2 mol%, and the weight average molecular weight in terms of standard polystyrene measured by GPC. Poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH)
A-2: P3HB3HH having a 3HH composition of 5.4 mol% and a standard polystyrene-equivalent weight average molecular weight of 620,000 obtained according to the method described in International Publication No. 2008/010296.

In the examples and comparative examples, the following talc was used as a filler.
B-1: Micro Ace K-1 (made by Nippon Talc)

(Differential scanning calorimetry evaluation)
An aluminum pan is filled with 4 to 10 mg of a resin sample, and the temperature is raised from 30 ° C. to 180 ° C. at a rate of 10 ° C./min under a nitrogen stream using a differential scanning calorie analyzer to obtain the resin sample when the resin sample is melted. In the heat absorption curve, the temperature at which the amount of heat absorption is maximized is defined as the melting point peak temperature, and the temperature at which the melting point peak ends on the higher temperature side than the melting point peak temperature and heat absorption is no longer recognized is defined as the end temperature on the high temperature side of the melting point peak. did.

(Evaluation of resin sheet thickness)
The thickness was measured at 10 points every 10 cm along the TD direction of the resin sheet using a caliper, and the arithmetic mean value of the thickness at the 10 points was calculated to obtain the thickness of the resin sheet.

(Evaluation of heat shrinkage rate)
As shown in FIG. 2, the resin sheet was cut into a size of 120 mm in the MD direction × 120 mm in the TD direction, and a square shape of 100 mm in the MD direction × 100 mm in the TD direction was marked in the center thereof. The resin sheet is placed on a paper coated with silica, placed in a dryer set at 160 ° C., heated for 10 minutes, cooled to room temperature, and then the length of the side of the square in the MD direction is measured. , The heating shrinkage rate was determined by the formula 1.
Equation 1: Heating shrinkage rate = ((length before heating (mm))-(length after heating (mm))) / (length before heating (mm)) × 10

(Drawdown evaluation)
A thermograph is attached to the center of a resin sheet 20 cm in the MD direction x 20 cm in the TD direction, and on a frame base of 20 cm in length x 20 cm in width x 50 cm in height with a square opening of 17.5 cm in length x 17.5 cm in width in the center. The resin sheet was fixed to the resin sheet, and the frame base was placed in an oven set at 160 ° C., and when the thermograph showed 140 ° C., the frame base 11 was taken out, and as shown in FIG. 4, from the fixed surface of the resin sheet. The vertical distance 13 to the lowest point 14 of the hanging resin sheet 12 was measured, and the drawdown was evaluated.

(Thermoforming method of resin sheet)
The resin sheet was thermoformed using a vacuum forming machine. First, the resin sheet is cut out to a side of 300 mm, fixed to a square mold, a thermo label (registered trademark) is attached to the center of the resin sheet, and then the thermo label (thermo label (registered trademark) is placed in a preheating room where the far infrared heater is set to 350 ° C. The resin sheet was preheated until the label (registered trademark) reached a predetermined temperature (preheating temperature). Next, the mold is pushed up from below the resin sheet, the mold is brought into contact with the resin sheet, vacuum is drawn from the holes provided at the bottom of the mold, and the resin sheet is formed into a container shape by following the mold. Then, the mold was released to obtain a molded product. The mold used for this evaluation is a rounded container with an opening of 110 mm square and a depth of 35 mm, the bottom is 80 mm square and has a rounded shape with R = 10 mm, and the bottom and side walls are also R. It had a curved portion of = 10 mm. A schematic diagram of the shape of the mold is shown in FIG.

(Evaluation of thermoformability)
Since the bottom corner of the molded product obtained by the above thermoforming was stretched to the maximum and the thickness became thin, the bottom corner and the center of the flat surface of the bottom of the container were cut out, and the respective thicknesses were caliper. The thickness ratio was calculated by the following formula 2 and evaluated according to the following criteria.
Equation 2: Thickness ratio = (thickness of bottom corner (mm)) / (thickness of bottom plane (mm))
◯: The thickness ratio is 0.7 or more ×: The thickness ratio is less than 0.7

(Measurement of dimensional change rate after thermoforming)
The width of the opening of the molded body was measured immediately after thermoforming and one week after thermoforming, and the dimensional change rate after thermoforming was obtained from Equation 3.
Equation 3: Dimensional change rate after thermoforming = ((width (mm) after one week)-(width (mm) immediately after molding)) / (width (mm) immediately after molding) × 100

<Example 1>
A-1, A-2, and B-1 were charged into the planetary extruder at the blending ratios shown in Table 1, and after melt-kneading at a set temperature of 140 ° C., the melt-kneaded resin was melt-kneaded with a roll diameter of 60 cm and a roll width of 1400 cm. A cooling roll with a set temperature of 80 ° C, which is formed into a sheet shape by sandwiching it between two rolls with a roll set temperature of 125 ° C and a roll rotation speed of 10 rpm, and the rotation speed is adjusted so that the draw ratio becomes 1.5 times. The sheet was cooled while being stretched in the MD direction, and the end portion in the width direction was slit to obtain a heat-molding resin sheet having a width of 1000 mm and a thickness of 0.3 mm.
The temperature of the resin coming out of the outlet of the planetary extruder at the time of sheet molding and the temperature of the resin sheet immediately after passing through the cooling roll was measured with a non-contact thermometer. In addition, differential scanning calorimetry and evaluation of the resin sheet were carried out to measure the melting point peak temperature and the end temperature on the high temperature side of the melting point peak. The evaluation results are shown in Table 1.
For the thermoforming evaluation of the resin sheet, a mold having a side of 300 mm was used, and the resin sheet was preheated so that the preheating temperature became 140 ° C., and thermoforming was performed. The evaluation results are shown in Table 1.

<Example 2>
A resin sheet for thermoforming was obtained in the same manner as in Example 1 except that the compounding ratio was changed, and differential scanning calorimetry evaluation and thermoforming evaluation were performed. The evaluation results are shown in Table 1.

<Example 3>
A resin sheet for thermoforming was obtained in the same manner as in Example 1 except that the compounding ratio was changed, and differential scanning calorimetry evaluation and thermoforming evaluation were performed. The evaluation results are shown in Table 1.

<Comparative Example 1>
A resin sheet for thermoforming was obtained in the same manner as in Example 3 except that the draw ratio was changed to 1.0 times, and differential scanning calorimetry evaluation and thermoforming evaluation were performed. The evaluation results are shown in Table 1.

[Manufacturing of poly (3-hydroxybutyrate) resin pellets]
A-1, A-2, and B-1 were dry-blended at the compounding ratios shown in Examples 4 to 6 or Comparative Example 2 in Table 2. The obtained resin material is put into a φ26 mm isodirectional twin-screw extruder in which the cylinder temperature and die temperature are set to 150 ° C., extruded, passed through a water tank filled with hot water at 45 ° C. to solidify the strands, and a pelletizer is used. Resin pellets were obtained by cutting.

<Example 4>
The cylinder temperature and die temperature of a φ90 mm single-screw extruder to which a T-die with a width of 1500 mm is connected are set to 160 ° C., the resin pellets are charged and extruded into a sheet with a T-die, and the first set temperature is 80. After cooling with a cooling roll at ° C, the sheet is cooled while being stretched in the MD direction with a second cooling roll having a set temperature of 60 ° C, whose rotation speed is adjusted so that the stretching ratio becomes 1.5 times, and then cooled in the width direction. By slitting the end portion, a resin sheet for thermoforming having a width of 1000 mm and a thickness of 0.3 m was obtained.
The temperature of the resin that came out from the outlet of the T-die during sheet molding and the temperature of the resin sheet immediately after passing through the second cooling roll were measured with a non-contact thermometer. In the same manner as in Example 1, differential scanning calorimetry evaluation and thermoforming evaluation of the resin sheet were performed. The evaluation results are shown in Table 2.

<Example 5>
A resin sheet for thermoforming was obtained in the same manner as in Example 4 except that the compounding ratio was changed, and differential scanning calorimetry evaluation and thermoforming evaluation were performed. The evaluation results are shown in Table 2.

<Example 6>
A resin sheet for thermoforming was obtained in the same manner as in Example 4 except that the compounding ratio was changed, and differential scanning calorimetry evaluation and thermoforming evaluation were performed. The evaluation results are shown in Table 2.

<Comparative Example 2>
A resin sheet for thermoforming was obtained in the same manner as in Example 6 except that the draw ratio was changed to 1.0 times, and differential scanning calorimetry evaluation and thermoforming evaluation were performed. The evaluation results are shown in Table 2.

In the thermoforming resin sheets of Examples 1 to 6 having a heat shrinkage rate of 2% or more, in the molded product molded from the resin sheet, the thickness of the bottom corner portion most stretched by thermoforming is other than that. It is not extremely thin as compared with the site, and it can be seen that the molded product can be suitably used as a container.

On the other hand, in the thermoforming resin sheets of Comparative Examples 1 and 2 in which the heat shrinkage rate was less than 2%, the thickness of the bottom corner portion of the molded product molded from the resin sheet was significantly larger than that of other portions. It became thin.

Further, it can be seen that the molded bodies of Examples 2, 3, 5 and 6 to which the filler is added have a smaller dimensional change rate after thermoforming than the molded bodies of Examples 1 and 4 to which the filler is not added. ..

11 Frame stand 12 Resin sheet hanging from the opening of the frame stand 13 Drawdown 14 The lowest point of the resin sheet

Claims (15)

A resin sheet for thermoforming containing a poly (3-hydroxybutyrate) resin.
A thermoforming resin sheet having a thermoforming resin sheet having a heat shrinkage rate of 2% or more in the MD direction and / or the TD direction measured by heating to 160 ° C. as the temperature indicated by the thermoforming resin sheet. The thermoforming resin sheet according to claim 1, wherein the poly (3-hydroxybutyrate) -based resin contains poly (3-hydroxybutyrate-co-3-hydroxyhexanoate). The thermoforming according to claim 1 or 2, further comprising a filler, wherein the content of the filler is 1 to 100 parts by weight with respect to 100 parts by weight of the poly (3-hydroxybutyrate) resin. Resin sheet. The thermoforming resin sheet according to claim 3, wherein the filler is an inorganic filler. The thermal molding according to claim 4, wherein the inorganic filler contains at least one selected from silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, and carbon black. Resin sheet. The thermoforming resin sheet according to claim 3, wherein the filler is an organic filler. Any of claims 1 to 6, wherein the difference between the melting point peak temperature in the differential scanning calorimetry of the poly (3-hydroxybutyrate) resin and the end temperature on the high temperature side of the melting point peak is 10 ° C. or higher and 70 ° C. or lower. The resin sheet for thermoforming according to item 1. The thermoforming resin sheet according to any one of claims 1 to 7, wherein the thermoforming resin sheet has a thickness of 0.1 to 1 mm. The thermoforming resin sheet according to any one of claims 1 to 8, wherein the drawdown of the thermoforming resin sheet measured by the following method is 10 cm or less.
Drawdown: The thermoforming resin sheet of 20 cm in the MD direction x 20 cm in the TD direction on a frame base of 20 cm in length × 20 cm in width × 50 cm in height having a square opening of 17.5 cm in length × 17.5 cm in width in the center. The distance in the vertical direction from the fixed surface of the thermoforming resin sheet to the lowest point when the temperature of the thermoforming resin sheet is heated to 140 ° C. The method for producing a thermoforming resin sheet according to any one of claims 1 to 9.
A step of melting the sheet raw material containing the poly (3-hydroxybutyrate) resin with an extruder and then molding it into a sheet, and
A manufacturing method comprising a step of stretching a molded sheet in a uniaxial direction or a biaxial direction at a stretching ratio of 1.1 times or more to obtain a resin sheet for thermoforming. The temperature of the sheet raw material and the thermoforming resin sheet is 40 ° C. until the sheet raw material containing the poly (3-hydroxybutyrate) resin is melted by an extruder and then stretched to obtain the thermoforming resin sheet. The production method according to claim 10, wherein the temperature is within the range of 165 ° C. or lower. The manufacturing method according to claim 10 or 11, wherein the molding into a sheet shape is carried out by sandwiching the molten sheet raw material between two or more rolls. The manufacturing method according to claim 10 or 11, wherein the molding into a sheet shape is carried out by extruding the molten sheet raw material from a T-die. A method for producing a molded product, which comprises a step of preheating the thermoforming resin sheet according to any one of claims 1 to 9 and then molding the resin sheet. 14. Claim 14 for preheating the thermoforming resin sheet to a temperature between the melting point peak temperature in the differential scanning calorimetry of the poly (3-hydroxybutyrate) resin and the end temperature on the high temperature side of the melting point peak. The method for manufacturing a molded product according to the above.

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