JPS6112941B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sintered body using a saponified ethylene-vinyl acetate copolymer and a method for producing the same. Conventional polymeric porous materials include polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polymethyl methacrylate, nylon, acrylonitrile-styrene copolymer,
Although materials made from various resins such as ABS resin and polyvinyl chloride have been developed, there are few porous materials that have both hydrophilicity and oil/solvent resistance. However, so-called formal sponge, which is made by formalizing polyvinyl alcohol, is known as a hydrophilic porous material, but this material is a sponge material with high elasticity, and its uses do not require much strength, such as cosmetic sponges. limited in use. The present invention provides a porous material that is hydrophilic, oil resistant, solvent resistant, and strong by sintering. The sintered body of the present invention is a saponified ethylene-vinyl acetate copolymer having an ethylene content of 10 to 60 mol% and a saponification degree of vinyl acetate component of 80 mol% or more, which is half the melting peak measured by a differential scanning calorimeter. Width of 5℃ or more 100-40% by weight and inorganic filler 0-60
It is a sintered body with a porosity of 25 to 95% by weight,
Such a sintered body is produced by filling particles made of the saponified ethylene-vinyl acetate copolymer (or the saponified copolymer and an inorganic filler) into a preheated mold, and then raising the temperature under pressure to form the particles. It is obtained by sintering at a temperature at which only the surface of the material melts, followed by cooling. The sintered body thus obtained has hydrophilicity, as well as water resistance, solvent resistance, oil resistance, and grease resistance, is beautiful, has a favorable surface condition, and has a hardness ranging from semi-hard to hard. you can choose,
Because of its high strength, it is extremely important for applications such as kerosene filters, gasoline strainers, drain rollers for X-ray film development, and ink rollers. A sintered body with such properties is difficult to obtain by using general thermoplastic resins, and with hydrophilic resins such as polyvinyl alcohol, the resin undergoes thermal decomposition during sintering, so it is completely unsatisfactory. cannot be obtained, and even if it were obtained, it cannot be used for the above-mentioned purposes because it lacks water resistance. In the present invention, the ethylene content is 10 to 60 mol%,
A saponified ethylene-vinyl acetate copolymer having a saponification degree of vinyl acetate component of 80 mol% or more is used as the raw material resin. If the ethylene content is less than 10 mol%, not only melting but also thermal decomposition will occur at the sintering temperature, and if the ethylene content exceeds 60 mol%, oil resistance and solvent resistance will be lacking. Also, if the degree of saponification is less than 80 mol%, oil resistance,
Due to insufficient solvent resistance and poor water resistance, dimensional changes and porosity changes are likely to occur. The saponified ethylene-vinyl acetate copolymer contains, in addition to each component of ethylene and vinyl acetate (or vinyl alcohol obtained by saponifying it), other copolymerizable monomer components, such as propylene,
Isobutene, α-octene, α-dodecene, α-
α-olefins such as octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, or parts thereof, fully alkyl esters, amides, nitriles, salts, anhydrides, olefinsulfonic acid or its salts, vinyl ethers,
It may also contain a small amount of vinyl ester other than vinyl acetate. Even if the saponified ethylene-vinyl acetate copolymer has the above composition, for the purpose of the present invention, the half width of the melting peak of the temperature rising melting curve measured by the differential scanning calorimeter of the resin is 5°C or more. is required.
The half width of the melting peak is thought to be mainly due to the distribution of crystal size, and the crystal size is influenced by the ethylene content, degree of saponification, randomness in the copolymer of ethylene and vinyl acetate, distribution of degree of polymerization, and saponification. Various values can be taken depending on requirements such as temperature distribution, but if this half width is less than 5°C, it becomes very difficult to control the sintering temperature and pressure. For example, during sintering, the entire particle may melt and the porosity becomes extremely small, or conversely, the fusion between the particles may be insufficient, resulting in a lack of strength. FIG. 1 shows a model of the heating melting curve of a saponified ethylene-vinyl acetate copolymer measured by a differential scanning calorimeter. The horizontal axis is temperature (℃), and the vertical axis is specific heat (cal/g・
℃). In the present invention, the peak temperature m is the melting point, and the temperature difference n-l between the two points that intersect the curve when a line is drawn parallel to the baseline from the intermediate point z after the x and y points in the figure is defined as the melting point. Let's define it as half width. However, a PerkinElmer differential scanning calorimeter was used, the sample was 10 mg, and the heating rate was 20°C/min.
shall be measured at In the present invention, a single saponified ethylene-vinyl acetate copolymer may be used as the saponified ethylene-vinyl acetate copolymer. but
It is more preferable to use two or more saponified ethylene-vinyl acetate copolymers together if the content is 80 mol% or more. When two or more resins are used together, the melting points of each resin may be the same or very close to each other, but preferably the melting points are 3°C or more apart, and the melting points are as shown in Figure 2.
The temperature difference between l ₁ - n ₂ (this is called the half-width when two or more melting peaks appear) is 5
The temperature should preferably be 8°C or higher, especially 8°C or higher. The blending ratio when two types of saponified ethylene-vinyl acetate copolymers are used together can be determined arbitrarily, but the weight ratio is 5:95 to 95:5, especially 10:90 to 90:
It is preferable to set it to 10. When three or more types are blended, it is preferable that the resin having the largest proportion accounts for 95% by weight or less, preferably 90% by weight or less of the entire resin. If necessary, an inorganic filler is added to the saponified ethylene-vinyl acetate copolymer. Inorganic fillers include glass fiber, carbon fiber, carbon black, calcium carbonate, talc, asbestos,
Diatomaceous earth, clay, kaolinite, glass beads, shirasu balloons, garnet, silica, calcined gypsum, calcium silicate, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, barium sulfate, magnesium carbonate, aluminum hydroxide, boron nitride, Examples include metal powder, Glauber's salt, and ammonium sulfate. The blending of inorganic fillers improves mechanical strength and rigidity, improves resistance to deformation, and improves water and solvent resistance, which is advantageous in terms of cost reduction. By using these materials, it is possible to reduce surface tension and impart electrical conductivity. The content of the inorganic filler should be limited to 0 to 60% by weight based on 100 to 40% by weight of the resin; if the proportion of the inorganic filler exceeds this range, the resulting sintered body will lack strength and become brittle. When blending an inorganic filler with a saponified ethylene-vinyl acetate copolymer, simply mixing the two powders together may result in lack of uniformity.
It is more preferable to mix the two and then supply it to an extruder, and pelletize or crush the extruded product to obtain a composition in which both are uniformly mixed. The size of the saponified ethylene-vinyl acetate copolymer particles or particles made of the resin and inorganic filler to be subjected to sintering may be determined arbitrarily, but at least 80% by weight of the particles should be 6 mesh sieve or below.
It is desirable for the product to have a particle size that falls within the range of 250 mesh sieve or higher. The particles are filled into a preheated mold. At this time, the particles may also be heated in advance. The temperature for preheating the mold is desirably set to a temperature in the range of 1/2 to 3/4 of the melting point of the saponified ethylene-vinyl acetate copolymer. For example, if the melting point of the saponified copolymer is 178°C, the temperature is set in the range of 178×1/2 to 178×3/4, that is, 89 to 133.5°C. When the preheating temperature is lower than the above range, the work takes a long time and is disadvantageous in terms of calorific value, making it unsuitable for industrial production.On the other hand, when it is higher than the above range, it is difficult to balance the temperature and pressure, and the porosity decreases. becomes difficult to control. Note that when one type of saponified ethylene-vinyl acetate copolymer is used, there is only one melting peak and the melting point is uniquely determined, but when two or more types of saponified ethylene-vinyl acetate copolymer are used together, there is a peak. There will be multiple melting points unless they overlap. In this case, it is sufficient that the preheating temperature corresponds to 1/2 to 3/4 of the melting point of at least one. However, if the amount of a certain type of saponified copolymer is small and the area of the dissolution peak is too small, it may be ignored and the melting point of the remaining saponified copolymer taken as the standard. Approximately 0.1~10Kg/cm ² after filling the particles into the mold
The temperature is increased to a predetermined temperature under this pressure range. The pressure can also be increased gradually during heating. It is appropriate that the temperature increase rate be 0.5 to 20°C/min. If the pressure is too low, no adhesion between the particles can be obtained, resulting in no strength, while if the pressure is too high, the porosity will be too low. If the heating rate is too slow, the entire particle will melt and no voids will be formed in the sintered body, while if it is too fast, it will be difficult to control the temperature, especially the temperature that stops the heating. The temperature is raised to a temperature at which only the surface of the particles melts, and sintering is carried out by maintaining this temperature for about 1 to 30 minutes, depending on the size and thickness of the object. The temperature at which only the surface of the particles melts is 30°C above the melting point of the saponified ethylene-vinyl acetate copolymer.
It refers to a temperature that is low or 30°C higher than the melting point. When there are two or more melting peaks, the sintering temperature should be within ±30°C of the melting point of at least one of them. However, if the area of the melting peak is too small, it is ignored and the melting point of the remaining saponified copolymer is taken as the standard. If the sintering temperature is lower than the above range, sintering will be insufficient and the strength of the molded product will be significantly inferior, while if the temperature is too high, the porosity may decrease and continuous pores may not be formed. A sintered body can be obtained by this method, but the sintering conditions should be selected so that the porosity is 25 to 95%. If the porosity is less than 25%, continuous pores will not be obtained, and porosity and wettability will occur. When the porosity exceeds 95%, the strength of the sintered body becomes insufficient. The porosity (%) is when the density of the porous body obtained by sintering is d (g/cc), and the true density of the polymer or composition having the same composition as the porous body is do (g/cc).
It can be calculated using the formula (1-d/do)×100. The pore diameter of the sintered body can be adjusted from 0.1 mμ to about 500μ. The shape of the sintered body can be arbitrarily selected depending on the mold. For example, cylindrical, disk-shaped, cylindrical,
In addition to rectangular tube shapes, plate shapes, prismatic shapes, concave shapes, wave shapes, etc., complex shapes can also be easily manufactured, and furthermore, these can be subjected to secondary processing such as bending and cutting. The sintered body of the present invention can be used for various purposes such as gas filtration, liquid filtration, waste oil collection, large oil separation, electric field diaphragm, and rollers. Specific examples include kerosene filters, gasoline strainers, food-related filters, drain rollers for X-ray film development, ink rollers, ink supply units for printers, pen nibs for writing instruments, mechanical parts, and bearings. Furthermore, when a conductive substance such as carbon fiber, carbon black, or metal powder is used as the inorganic filler, it can also be used as a wall material for an anechoic chamber. Next, the sintered body of the present invention and its manufacturing method will be further explained by giving examples. Example 1 A saponified ethylene-vinyl acetate copolymer with an ethylene content of 32 mol% and a degree of saponification of the vinyl acetate component of 98.5 mol%, with a melting point of 178°C and a melting peak half width of 7°C, was crushed into pellets using a crusher. Shattered to 125
Particles of ~297μ (48 mesh below to 120 mesh above) were sieved. These particles were filled into a pipe-shaped mold with an outer diameter of 40 mm and an inner diameter of 20 mm that had been preheated to 120°C, and the temperature was increased to 175°C at a rate of 2°C/min while pressurizing at 2 kg/ ^cm2 . After holding for a minute, the mold was cooled and a 40 mm long pipe-shaped sintered product was taken out from the mold. The porosity of this sintered body was 45%. The properties of the sintered body thus obtained are shown in Table 1. Despite being hydrophilic, it had excellent water resistance, trichlene resistance, and gasoline resistance, as well as good mechanical strength. Control example 1 Polyvinyl alcohol (polymerization degree 1700, saponification degree
Sintering was attempted in the same manner as in Example 1 using particles of 125 to 297μ (99.0 mol%), but the sintering temperature was 175°C.
At 185℃, 195℃, 205℃, no fusion occurred between particles.
The degree of fusion was poor even at 215°C and 225°C, and thermal decomposition occurred simultaneously with fusion, and the resulting sintered body was colored yellow or brown, and its strength was extremely low due to deterioration. Control Example 2 Sintering molding was attempted in the same manner as in Example 1 using saponified ethylene-vinyl acetate copolymer particles (125-297μ) having the same composition as Example 1, but with a melting point of 165°C and a half-width of 4°C. . However, if the sintering temperature is raised enough to achieve sufficient fusion between the particles, the entire particle will melt and the porosity will become extremely small, whereas if the sintering temperature is lowered, the adhesion between the particles will be significantly reduced. They were in short supply and could only obtain extremely fragile materials. Control example 3 Density 0.960, melt index 0.2, particle size 70~
Using 100μ high-density polyethylene fluid, mold preheating temperature 100℃, heating rate 5℃/min, pressure 4Kg/
cm ² , sintering temperature of 160° C., and sintering time of 12 minutes. The properties of the obtained sintered body with a porosity of 37% are shown in Table 1, and it was found to be poor in trichlene resistance, gasoline resistance, and hydrophilicity. Control example 4 Using polymethyl methacrylate particles with a viscosity of 150 to 220μ, mold preheating temperature 60℃, temperature increase rate 1℃/
min, pressure 2Kg/cm ² , sintering temperature 110℃, sintering time 15
The sintering process was carried out under the following conditions. Obtained porosity
The properties of the 35% sintered body are shown in Table 1, and it was found that the trichlene resistance, gasoline resistance, and hydrophilicity were poor. Example 2 65 parts by weight of the saponified ethylene-vinyl acetate copolymer particles used in Example 1 and 35 parts by weight of talc powder were mixed in a Henshil mixer, fed into an extruder to form pellets, and then the pellets were crushed. and 125
Particles of ~297μ (48 mesh below to 120 mesh above) were sieved. The melting point and half width of the particles were the same as in Example 1. Using these particles, sintering was carried out under the same conditions as in Example 1. The porosity of the sintered body was 48%. The properties of the sintered body thus obtained are shown in Table 1.

【table】

[Table] Example 3 55 of a saponified ethylene-vinyl acetate copolymer with an ethylene content of 42 mol% and a degree of saponification of the vinyl acetate component of 99.0 mol%, a melting point of 165°C, and a half-width of the melting peak of 8°C. The sieved product under the mesh sieve or on the 170 mesh sieve is preheated to approximately 90°C, and the particles are preheated to 100°C with an outer diameter of 30 mm and an inner diameter of 20 mm.
The material was filled into a pipe-shaped mold with a diameter of 1.5 mm, and the temperature was raised to 160 °C at a rate of 3 °C/min while pressurizing at 4 kg/cm ^2. After sintering by keeping at this temperature for 12 minutes, the mold was cooled. Then, a pipe-shaped sintered body with a length of 300 mm was taken out from the mold. The porosity of this sintered body was 43%. The properties of the sintered body thus obtained are shown in Table 2. Example 4 80 parts by weight of the saponified ethylene-vinyl acetate copolymer powder used in Example 3 and 20 parts by weight of calcium carbonate fine powder
After mixing parts by weight in a Henschel mixer, the pellets are fed to an extruder to form pellets, and then the pellets are crushed to a size of 125 to 297μ (under a 48 mesh sieve).
The particles were sieved (on a 120 mesh sieve). The melting point and half width of this particle were the same as in Example 3. Using these particles, sintering was carried out under the same conditions as in Example 1. The porosity of the sintered body was 47%. The results are shown in Table 3. Example 5 The pulverized pellets of saponified ethylene-vinyl acetate copolymer used in Example 1 and the saponified ethylene-vinyl acetate copolymer powder used in Example 3 were calculated by weight.
After mixing in a Henschel mixer at a ratio of 80:20, the mixture was fed to an extruder to form pellets, and the pellets were then ground and sieved to obtain particles of 125-297μ. These particles have melting peaks at 178°C and 165°C, and the half-width corresponding to the temperature difference between l ₁ - n ₂ in Figure 2 is 20°C.
It was hot. Using these particles, the particle preheating temperature was 110℃, the mold preheating temperature was 120℃, the heating rate was 2℃/min, and the pressure was 5Kg/min.
cm ² , sintering temperature of 190° C., and sintering time of 13 minutes. The porosity of the sintered body was 47%. The results are shown in Table 2. Example 6 Add glass fiber to 70 parts by weight of the resin mixture of Example 5.
30 parts by weight were mixed, pelletized, crushed, and sieved. The melting peak and half width were the same as in Example 5. Using these particles, the particle preheating temperature was 125℃, the mold preheating temperature was 135℃, the heating rate was 4℃/min, and the pressure was 6Kg/min.
cm ² , sintering temperature of 200° C., and sintering time of 14 minutes. The porosity of the sintered body was 46%. The results are shown in Table 2.

【table】

【table】 [Brief explanation of the drawing]

Figure 1 is a relational diagram showing an example of the temperature rise melting curve measured by a differential scanning calorimeter for a saponified ethylene-vinyl acetate copolymer, and Figure 2 is a diagram showing an example of the temperature rise melting curve of a saponified ethylene-vinyl acetate copolymer. It is a relationship diagram showing an example of a temperature rise melting curve when blended.

Claims (1)

[Scope of Claims] 1 A saponified ethylene-vinyl acetate copolymer having an ethylene content of 10 to 60 mol% and a degree of saponification of the vinyl acetate component of 80 mol% or more, the half width of the melting peak measured by a differential scanning calorimeter. A sintered body with a porosity of 25 to 95%, consisting of 100 to 40% by weight of a filler with a temperature of 5°C or higher and 0 to 60% by weight of an inorganic filler. 2 The saponified ethylene-vinyl acetate copolymer is
The sintered body according to claim 1, which is a mixture of two or more saponified ethylene-vinyl acetate copolymers whose melting points (melting peak temperatures) are 3° C. or more apart. 3. Particles consisting of a saponified ethylene-vinyl acetate copolymer with an ethylene content of 10 to 60 mol%, a degree of saponification of the vinyl acetate component of 80 mol% or more and 100 to 40% by weight, and an inorganic filler of 0 to 60% by weight were preheated. A sintered body with a porosity of 25 to 95% is obtained by filling it into a mold, raising the temperature under pressure, sintering at a temperature that melts only the surface of the particles, and then cooling. A method for manufacturing a sintered body. 4. The manufacturing method according to claim 3, characterized in that the particles have a particle size such that 80% by weight or more is contained in the range from below a 6-mesh sieve to above a 250-mesh sieve. 5 Set the preheating temperature of the mold to 1/2 to 1/2 of the melting point of the resin.
The manufacturing method according to claim 3, characterized in that the temperature is set in a range of 3/4. 6 The temperature at which only the surface melts is 30° below the melting point of the resin.
The manufacturing method according to claim 3, wherein the temperature is 30°C lower than the melting point or 30°C higher than the melting point. 7 As a saponified ethylene-vinyl acetate copolymer, two or more types of ethylene-vinyl acetate copolymer having melting points separated by 3°C or more are used.
The manufacturing method according to claim 3, characterized in that a saponified vinyl acetate copolymer is used in combination.