Porous material, and method for manufacturing a porous material

Abstract

To provide a novel porous material with shape memory properties. [Solution] This technology first provides a shape-memory porous body obtained by removing a pore-forming material from a resin composition containing a pore-forming material and crosslinking it. This technology also provides a method for manufacturing a shape-memory porous body, comprising the steps of (I) removing the pore-forming material from a resin composition containing a pore-forming material, and (II) crosslinking the resin composition from which the pore-forming material has been removed after step (I).

Description

Technical Field

[0001] The present technology relates to a porous body and a method for manufacturing the porous body.

Background Art

[0002] Currently, porous bodies made of resin are used in various fields. For example, they are used in functional separation membranes such as filters and filtration membranes, water retention materials, water stop materials, sustained release materials, stamp pads using solvent-type ink, members for absorbing and holding organic solvents, bleeding pad materials, cosmetic tools, medical tools, abrasive materials, or cleaning materials, etc.

[0003] In addition, technologies for imparting additional properties to porous bodies are also being developed according to the uses of the porous bodies. For example, in Patent Document 1, as a cosmetic porous elastomer that does not change color even with ultraviolet rays or the like and has good skin feel, etc., a mixture of a gas-phase metallocene-based polyethylene resin and a metallocene elastomer as an ethylene-α-olefin copolymer resin is disclosed, wherein the metallocene elastomer is blended in an amount of 25 to 40 parts by weight with respect to 100 parts by weight of the gas-phase metallocene-based polyethylene resin.

[0004] Also, in Patent Document 2, from a heat mixture of at least one kind of thermoplastic resin, a water-soluble foaming agent that is thermally stable and can maintain its shape at the temperature at which the thermoplastic resin melts, a water-soluble polymer compound that acts as a lubricant, and a functional substance that imparts a desired function to the final product foam, the water-soluble foaming agent and the water-soluble polymer compound are extracted and removed by water, and a foam containing the functional substance having a three-dimensional interconnected bubble structure in which the functional substance is uniformly dispersed is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] As mentioned above, technologies for imparting new properties to porous materials are being developed, and there is a demand for technologies to impart shape memory as one of these new properties. However, this field of technology is still immature, and there is a need for the development of new technologies.

[0007] Therefore, the main objective of this technology is to provide a novel porous material with shape memory properties. [Means for solving the problem]

[0008] In this technology, first, the pore-forming material is removed from a resin composition containing a pore-forming material. The present invention provides a porous material with shape memory properties in a crosslinked state. In the porous material relating to this technology, the shape memory property may be exhibited in response to temperature changes. In the porous material relating to this technology, the crosslinking may be electron beam crosslinking. In the porous material relating to this technology, the gel fraction may be 65% or more.

[0009] This technology also includes a step (I) of removing the pore-forming material from a resin composition containing the pore-forming material, After step (I), step (II) is performed to crosslink the resin composition from which the pore-forming material has been removed, The present invention provides a method for manufacturing a porous body having shape memory properties.

[0010] In this specification, "shape memory" refers to the property of a material that, while maintaining a specific shape as a stable state, recovers to its original shape after being deformed into an arbitrary shape by applying an external force, and then being heated above a certain temperature. [Modes for carrying out the invention]

[0011] The following describes a preferred form for implementing this technology. The embodiments described below are examples of typical embodiments of this technology, and any combination of these embodiments is possible. Furthermore, this does not mean that the scope of this technology will be narrowed.

[0012] 1. Porous material The porous material according to this technology is obtained by removing the pore-forming material from a resin composition containing the pore-forming material, and is in a crosslinked state, possessing shape memory properties. In addition to the resin component and pore-forming material, a water-soluble polymer acting as a lubricant and other components depending on the purpose can be used in the manufacture of the porous material according to this technology. The components used in the manufacture of the porous material according to this technology will be described in detail below.

[0013] (1) Resin components The resin components related to this technology are not particularly limited, but examples include hydrocarbon resins, epoxy resins, acrylic resins, polyester resins, etc., and it is possible to use one or more of these in combination. In addition, examples include styrene-butadiene rubber, ethylene propylene-diene rubber, natural rubber, poly(ethylene-co-vinyl acetate) (EVA), polydimethylsiloxane (silicone), etc.

[0014] In this specification, "hydrocarbon resin" refers to a resin whose main skeleton is composed of hydrocarbons and falls under the category of thermoplastic resins. Examples of hydrocarbon resins include hydrocarbon resins containing octene as a unit structure (which may be cyclic or acyclic; including polycyclooctene), polyethylene, polypropylene, polystyrene, polyurethane, polybutadiene, polyisobutene, polyvinyl chloride (PVC), polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate (PMMA), polynorbornene, styrene-butadiene copolymer, etc., and these can be used individually or in combination of two or more.

[0015] In this technology, among these, a hydrocarbon resin containing octene as a unit structure is particularly preferable. Further, the polyoctenamer may contain trans-polyoctenamer and / or cis-polyoctenamer. Specifically, the structures described in the following chemical formula (1) and / or the following chemical formula (2) can be mentioned, and it is more preferable to contain both of them.

[0016]

Chemical formula

[0017]

Chemical formula

[0018] Furthermore, in this technology, commercially available products may be used, and such hydrocarbon resins are sold, for example, by Daicel Degussa Co., Ltd. under the trade name "VESTENAMER (registered trademark)".

[0019] The amount of the resin component used in the production of the porous body according to this technology can be freely set according to the purpose. The lower limit of the amount of the resin component used in the raw material of the porous body is, for example, 5% by volume or more, preferably 10% by volume or more, and more preferably 15% by volume or more. The upper limit of the amount of the resin component used in the raw material of the porous body is, for example, 50% by volume or less, preferably 45% by volume or less, and more preferably 40% by volume or less.

[0020] (2) Pore-forming material The pore-forming material that can be used in this technology is preferably soluble in water, alcohol, or an aqueous solution of alcohol (preferably water), and is stable even when the resin melts. Specifically, examples include inorganic substances such as NaCl, KCl, CaCl, NH4Cl, NaNO3, and NaNO2; organic substances such as TME (trimethylolethane), trimethylolpropane, trimethylolbutane, sucrose, soluble starch, sorbitol, glycine, and sodium salts of various organic acids (e.g., malic acid, citric acid, glutamic acid, succinic acid, etc.). It is also possible to use one or more of these in combination.

[0021] In this technology, it is particularly preferable to use inorganic materials among these, and among inorganic materials, it is particularly preferable to use NaCl.

[0022] The average particle size of the pore-forming material can be freely set as long as it does not impair the function or effect of this technology. The lower limit of the average particle size of the pore-forming material is, for example, 10 μm or more, preferably 20 μm or more, and more preferably 30 μm or more. By setting the lower limit of the average particle size of the pore-forming material within this range, the size of the pores in the porous body can be controlled to a certain level or higher, and a porous body with a smooth surface can be provided.

[0023] The upper limit of the average particle size of the pore-forming material is, for example, 300 μm or less, preferably 250 μm or less, and more preferably 200 μm or less. By setting the upper limit of the average particle size of the pore-forming material within this range, the size of the pores in the porous material can be controlled to a certain level or less, and a stable porous material can be obtained.

[0024] Furthermore, the "average particle size of the porosity-forming material" refers to the average particle size in the mixed state when two or more porosity-forming materials with a single peak are mixed. In this technology, the "average particle size" is the particle size at which the cumulative frequency reaches 50% (D-50) in the particle size distribution measured by laser diffraction.

[0025] The amount of pore-forming material used in the production of the porous body according to this technology can be freely set as long as it does not impair the function or effect of this technology. The lower limit of the amount of pore-forming material used in the raw material of the porous body is, for example, 40% by volume or more, preferably 45% by volume or more, and more preferably 50% by volume or more. The upper limit of the amount of pore-forming material used in the raw material of the porous body is, for example, 85% by volume or less, preferably 75% by volume or less, more preferably 70% by volume or less, even more preferably 65% ​​by volume or less, and particularly preferably 60% by volume or less.

[0026] (3) Water-soluble polymer compound In the production of the porous material relating to this technology, a water-soluble polymer compound that acts as a lubricant may be used. Specifically, examples include polyethylene glycol, polyethylene oxide, polyethylene glycol diacrylate, polyethylene glycol dioleate, and polyethylene glycol derivatives such as polyethylene glycol diacetate, and it is possible to use one or more of these in combination.

[0027] In this technology, polyethylene glycol is particularly preferred among these materials. This is because polyethylene glycol has a high melt flow and high water solubility. When molding is performed by extrusion molding, the number average molecular weight of polyethylene glycol is preferably 2,000 to 30,000, more preferably 5,000 to 25,000, and even more preferably 15,000 to 25,000.

[0028] The amount of water-soluble polymer compound used in the production of porous materials according to this technology can be freely set as long as it does not impair the function or effect of this technology. The lower limit of the amount of water-soluble polymer compound used in the raw materials of the porous material is, for example, 10% by volume or more, preferably 15% by volume or more, and more preferably 20% by volume or more. The upper limit of the amount of water-soluble polymer compound used in the raw materials of the porous material is, for example, 55% by volume or less, preferably 45% by volume or less, more preferably 40% by volume or less, even more preferably 35% by volume or less, and particularly preferably 30% by volume or less.

[0029] (4) Others The porous material relating to this technology may be freely selected to contain one or more other components that can be used in general porous materials, as long as they do not impair the function or effect of this technology. For example, it may contain any components such as fillers, colorants, flame retardants, plasticizers, antistatic agents, antioxidants, ultraviolet absorbers, and antifungal agents.

[0030] 2. Method for manufacturing porous materials The method for manufacturing a porous body according to this technology is a method that involves (I) removing a pore-forming material from a resin composition containing the pore-forming material, and (II) crosslinking the resin composition from which the pore-forming material has been removed after step (I). In the method for manufacturing a porous body according to this technology, by processing the porous body before crosslinking, the electron beam can easily penetrate into the interior of the porous body, making step (II) easier.

[0031] (1) Process (I) Step (I) is a step of extracting and removing the pore-forming material from a resin composition containing the pore-forming material. In this technology, other steps performed in general porous material manufacturing methods can be freely combined, as long as they do not impair the function and effect of this technology. For example, it can be manufactured by extracting and removing the pore-forming material and the water-soluble polymer compound from a molded body of a mixture of a resin component and, if necessary, other components mixed with the pore-forming material and a water-soluble polymer compound. Heating may be performed during the mixing as needed. In addition, each raw material of the porous material can be divided and mixed as needed.

[0032] More specifically, first, the resin components to be used as raw materials, and other components as needed, are mixed and kneaded in a predetermined mixing ratio using predetermined equipment. Then, this mixture is mixed and kneaded with one or more types of pore-forming materials and water-soluble polymer compounds in a predetermined mixing ratio using predetermined equipment to obtain a mixture. Next, the obtained mixture is molded into a molded body of a predetermined shape using an extruder or the like. The obtained molded body is then immersed in an extraction solvent at a predetermined temperature to extract and remove the pore-forming materials and water-soluble polymer compounds, thereby obtaining a porous body with numerous fine bubbles. The type of extraction solvent that can be used in this technology is not particularly limited and can be freely selected depending on the type of pore-forming material and water-soluble polymer compound used. Examples of extraction solvents include water.

[0033] For mixing and kneading the resin components, porosity-forming agents, and water-soluble polymer compounds mentioned above, kneading equipment such as laboplast mills, single-screw or twin-screw extruders, kneaders, pressure kneaders, conkneaders, Banbury mixers, Henschel mixers, and rotor mixers can be used. No special equipment is required for this kneading, and the kneading speed is not particularly limited. The temperature during kneading can be freely set depending on the melting point of the resins used. The kneading time depends on the physical properties of the mixture, but it is sufficient as long as the mixture is thoroughly mixed and kneaded. The kneaded raw materials can be molded into desired shapes by extrusion, injection molding, pressing, rolling, blow molding, etc.

[0034] The molded body, formed into the desired shape, is immersed in a solvent such as water for a predetermined time (depending on the shape and thickness of the molded body, for example, 24 to 48 hours) to extract and remove the pore-forming material and the water-soluble polymer compound. While any immersion method is acceptable, extraction and removal by immersion in water is preferred, as it brings the entire mixture into contact with the solvent. The temperature of the water used is not particularly limited as long as it is lower than the melting point of the resin used, but warm water at 15°C to 60°C may be used for efficient removal of the water-soluble substances.

[0035] As mentioned above, the porous material related to this technology does not use a foaming agent, so it does not generate harmful substances (such as ammonia), thereby improving safety and reducing environmental impact.

[0036] (2) Process (II) Step (II) is a step of crosslinking the resin composition after step (I) from which the pore-forming material has been removed. The crosslinking method may be physical crosslinking or chemical crosslinking. Examples of physical crosslinking include electron beam crosslinking, thermal crosslinking, ultraviolet crosslinking, pressure crosslinking, ultrasonic crosslinking, and tensile crosslinking. Examples of chemical crosslinking include crosslinking using a crosslinking agent, crosslinking by radical polymerization, vinyl crosslinking, ester crosslinking, and amide crosslinking.

[0037] In this technology, physical crosslinking is particularly preferred, and among physical crosslinking methods, electron beam crosslinking is particularly preferred. By using this crosslinking method, the generation of volatile organic compounds (VOCs) derived from the crosslinking agent can be suppressed, thus being environmentally friendly.

[0038] When performing electron beam crosslinking, the total irradiation dose can be freely set according to the purpose. In this technology, the upper limit of the total electron beam irradiation dose is not particularly limited, but for example, it can be 1000 kGy or less, preferably 800 kGy or less, more preferably 700 kGy or less, and even more preferably 600 kGy or less. Also, the lower limit of the total electron beam irradiation dose is not particularly limited, but for example, it can be 10 kGy or more, preferably 50 kGy or more, and more preferably 80 kGy or more.

[0039] 3. Physical properties of porous materials (1) Cell diameter The cell diameter of the porous material relating to this technology can be freely set as long as it does not impair the function or effect of this technology. The upper limit of the cell diameter of the porous material relating to this technology is not particularly limited, but for example, it is 300 μm or less, preferably 250 μm or less, and more preferably 200 μm or less. Setting the upper limit of the cell diameter of the porous material within this range makes it easy to manufacture a porous material of excellent quality. The lower limit of the cell diameter of the porous material is not particularly limited, but for example, it is 10 μm or more, preferably 20 μm or more, and more preferably 30 μm or more. Setting the lower limit of the cell diameter of the porous material within this range makes it easy to manufacture a porous material of excellent quality.

[0040] In this technology, the cell diameter is the value calculated using the method described in the examples below.

[0041] (2) Porosity The upper limit of the porosity of the porous material relating to this technology is not particularly limited, but for example, it is 90% or less, preferably 85% or less, and more preferably 80% or less. Setting the upper limit of the porosity of the porous material within this range prevents a decrease in the formability of the porous material and facilitates the manufacture of porous materials of excellent quality. The lower limit of the porosity of the porous material is not particularly limited, but for example, it is 50% or more, preferably 60% or more, and more preferably 70% or more. Setting the lower limit of the porosity of the porous material within this range improves solvent impregnation, and for example, when the porous material is used as a cleaning material, the cleaning solvent can penetrate sufficiently into the interior of the porous material, improving the cleaning effect.

[0042] In this technology, the porosity of the porous material is the value calculated using the method described in the examples below.

[0043] (3) Gel fraction The gel fraction of the porous material according to this technology can be freely set as long as it does not impair the function or effect of this technology. The upper limit of the gel fraction of the porous material according to this technology is not particularly limited, but for example, it is 95% or less, preferably 90% or less. The lower limit of the gel fraction of the porous material is not particularly limited, but for example, it is 65% or more, preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. By setting the lower limit of the gel fraction of the porous material within this range, a decrease in the strength of the porous material can be prevented and physical stability can be ensured. Shape memory properties can also be exhibited.

[0044] In this technology, the gel fraction is a value measured in accordance with JIS K6796.

[0045] (4) DSC peak temperature and shape memory The DSC peak temperature and shape memory properties of the porous material related to this technology can be freely set as long as they do not impair the function or effect of this technology. In this specification, "DSC peak temperature" refers to the temperature at which solidification or softening of the material occurs, and in cross-linked materials, shape memory properties are exhibited. Therefore, in this technology, shape memory properties are exhibited in response to temperature changes, and shape memory properties are exhibited at temperatures above the DSC peak temperature.

[0046] In this technology, the lower limit of the DSC peak temperature is not particularly limited, but it can be, for example, 35°C or higher. Since the porous material related to this technology returns to its original state when a certain temperature is applied, it helps to solve the transportation problem unique to porous materials (i.e., the problem of high transportation costs due to its light weight).

[0047] In this technology, the DSC peak temperature is the value measured by the method described in the examples below. Shape memory was determined by visually checking whether the porous material returned to its original shape after being deformed by raising the temperature above the DSC peak temperature, solidifying it by lowering the temperature below the DSC peak temperature, and then raising the temperature above the DSC peak temperature again.

[0048] 4. Applications of porous materials The porous material related to this technology can be used in a wide range of applications in any field, thanks to its high quality. For example, this technology allows it to be used as a sealing material, taking advantage of its shape memory properties.

[0049] Furthermore, this technology can also employ the following configurations. [1] A resin composition containing a pore-forming material, from which the pore-forming material is removed, A porous material with shape memory properties in a cross-linked state. [2] The porous body according to [1], wherein the shape memory property is exhibited in response to temperature changes. [3] The porous body according to [1] or [2], wherein the crosslinking is electron beam crosslinking. [4] A porous body according to any one of [1] to [3], wherein the gel fraction is 65% or more. [5] A step (I) of removing the pore-forming material from a resin composition containing the pore-forming material, After step (I), step (II) is performed to crosslink the resin composition from which the pore-forming material has been removed, A method for manufacturing a porous body having shape memory properties. [Examples]

[0050] The present technology will be described in more detail below based on the following examples. The examples described below are representative examples of the present technology and should not be interpreted as narrowing the scope of the present technology.

[0051] <Test Example 1> (1) Manufacturing of porous materials After weighing the raw materials shown in Tables 1 to 3 below, they were kneaded in a laboplast mill (temperature: 120°C, time: 5 min, rotation speed: 50 rpm). The kneaded mixture was then hot-pressed in a hand press (temperature: 120°C, time: 5 min), cooled with water, and immersed in water to allow the pore-forming agent and water-soluble polymer compound to dissolve overnight (temperature: approximately 25°C). The mixture was then dried to produce each porous material before crosslinking.

[0052] Subsequently, electron beam irradiation was performed using an electron beam irradiation device manufactured by NHV Corporation under the crosslinking conditions shown in Tables 1 to 3 below, to obtain each crosslinked porous material.

[0053] (2) Measurement and evaluation of physical properties The physical properties of each porous material manufactured were measured and evaluated using the following methods.

[0054] [Formability] In porous materials after the elution of pore-forming materials and water-soluble polymer compounds but before crosslinking, those that did not shrink (no change in thickness) were judged as "○", and those that did shrink (change in thickness) were judged as "×".

[0055] [Cell diameter] The cell diameter (μm) was calculated based on the particle size of the sodium chloride (NaCl) used as the raw material.

[0056] [Crosslinking conditions] The crosslinking conditions (total electron beam irradiation dose (kGy)) were varied for each porous material, and the surface of each porous material was observed visually. Materials that showed no change in the surface after electron beam irradiation were marked with "○", and those that showed a change in the surface (for example, those with a sticky surface) were marked with "×".

[0057] [Porosity] The porosity (%) was calculated using the following formula: the apparent density of each porous material, measured in accordance with JIS K7222, was divided by the density of the resin component, this divisor was subtracted from 1, and the result was multiplied by 100 to obtain the percentage. Porosity (%) = {1 - (Apparent density of porous material) ÷ ​​(Density of resin component)} × 100 (%)

[0058] [Gel fraction] The gel fraction (%) was measured in accordance with JIS K6796.

[0059] [DSC peak temperature and shape memory properties] The DSC peak temperature (°C) was measured using a Hitachi High-Tech Science Corporation DSC7000X under the following conditions: temperature 0°C → 200°C → 0°C → 200°C (2nd run), heating rate: 10°C / min, and atmosphere: N2250mL. The value obtained during the 2nd run was defined as the DSC peak temperature. Furthermore, shape memory properties were assessed by first deforming a porous material by raising its temperature above the DSC peak temperature, then solidifying it by lowering the temperature below the DSC peak temperature, and finally raising the temperature above the DSC peak temperature again. The results were visually checked to see if the material returned to its original shape. Materials exhibiting shape memory were marked with a "○" and those lacking shape memory were marked with a "×".

[0060] [Heat resistance evaluation] For heat resistance evaluation, each porous material was exposed to 150°C for 3 minutes. Materials that showed no change in shape were marked with "○", those that showed partial deformation were marked with "△", and those that completely melted were marked with "×".

[0061] (3) Results The results are shown in Tables 1 to 3 below.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] (4) Discussion As shown in Tables 1 to 3 above, Examples 1 to 9, which are porous bodies obtained by removing the pore-forming material from a resin composition containing the pore-forming material and are in a crosslinked state, exhibited shape memory properties, high gel fraction, and excellent heat resistance. On the other hand, Comparative Examples 1 to 3, which are in an uncrosslinked state, lacked shape memory properties, had a low gel fraction, and exhibited poor heat resistance. Furthermore, Comparative Example 4 did not form a porous body. In addition, Comparative Example 5 was not irradiated with an electron beam, resulting in poor evaluations of shape memory properties, gel fraction, and heat resistance.

Claims

1. A resin composition containing a pore-forming material, from which the pore-forming material is removed, A porous material with shape memory properties in a cross-linked state.

2. The porous body according to claim 1, wherein the shape memory property is exhibited in response to temperature changes.

3. The porous body according to claim 1, wherein the crosslinking is electron beam crosslinking.

4. The porous body according to claim 1, wherein the gel fraction is 65% or more.

5. A step (I) of removing the pore-forming material from a resin composition containing the pore-forming material, After step (I), step (II) is performed to crosslink the resin composition from which the pore-forming material has been removed, A method for manufacturing a porous body having shape memory properties.

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