JPS60243156A - Compounded composition of modified acicular crystal of gypsum and synthetic resin - Google Patents

Abstract

PURPOSE:To obtain the titled compounded composition having excellent and balanced tensile strength, impact strength, rigidity, dimensional stability, etc., by mixing a synthetic resin with acicular crystal of gypsum wherein the average diameter and the absorption of water per unit surface area of the crystal are lower than specific respective values. CONSTITUTION:Gypsum dihydrate having specific characteristics is used as a raw material, and is added with preferably fine powder of hydrated gypsum dihydrate. The mixture is dispersed in water at a concentration of 0.3-30wt%, and the resultant aqueous slurry is heated under pressure in an autoclave with agitation to obtain acicular crystal of alpha-type gypsum hemihydrate. The crystal is dehydrated, separated, dried and calcined at 400-700 deg.C, and the obtained acicular crystal of II-type gypsum anhydride having an average particle diameter of <=1.2mum and a water-absorption per unit surface area of about <=0.3mg/m<2>, preferably <=0.265mg/m<2> and free from granules or agglomerates having a diameter of about >=20mum, is added to a synthetic resin, especially to polyvinyl chloride resin or polyolefin resin in an amount of 5-75wt%.

Description

Detailed Description of the Invention The present invention provides gypsum needle crystals (α-type hemihydrate gypsum needle crystals, l-type anhydrite gypsum needle crystals, and ■-type aqueous gypsum needle crystals) suitable for compounding with synthetic resins. (general term for) and a synthetic resin.

Gypsum needles and their industrial utility are known from Japanese Patent Application Laid-Open No. 49-80626.

Gypsum needle crystals are expected to be used, for example, as a filler for paper making, a heat insulating material, or a reinforcing material for organic polymers. Of course, the properties expected of gypsum needle crystals vary depending on the application, but the mechanical properties such as elastic modulus and strength when composited with organic polymers, especially thermoplastic resins, are important.

One of the factors that determines these mechanical properties is the aspect ratio (vertical/width ratio) of the gypsum needles in the composite. Generally, as shown in the short fiber reinforcement theory, the larger the aspect ratio, the higher the elastic modulus. Tensile strength etc. are improved. Therefore, preferred gypsum needles for reinforcing the thermoplastic resin are those having a large aspect ratio in the composite. In other words, strong gypsum needle crystals that are difficult to break during the process of kneading and compounding thermoplastic resin and gypsum needle crystals are expected. However, the reinforcing properties of gypsum needle crystals are insufficient. Especially for polyvinyl chloride resin,
When gypsum needle crystals are cross-dispersed, the aspect ratio of the gypsum needle crystals in the composite becomes smaller, so although the elastic modulus and dimensional stability (coefficient of thermal expansion) improve, mechanical strength reinforcement is small. . In particular, in the case of tensile strength, there is no reinforcing property and it is lower than the base strength (strength of only polyvinyl chloride resin without gypsum needle crystals added).

On the other hand, one of the important physical properties of polyvinyl chloride resin composites is impact strength. In the case of impact strength as well, when the above-mentioned gypsum needle crystals are cross-dispersed, the strength is significantly lower than the base strength.

Furthermore, it has been impossible to simultaneously improve the tensile strength (approaching the base strength) and the impact strength in the face acicular crystals.

In view of the above points, the present inventors have carried out intensive research and have found that a new gypsum needle crystal has a tensile strength and impact strength comparable to that of polyvinyl chloride resin when composited with polyvinyl chloride resin. successfully created.

In other words, the rigidity, dimensional stability, etc. of the molded body composited with the IJm vinyl resin are improved to the same level or higher than those of the conventional composite of gypsum needle crystals, while the tensile strength and impact strength of the molded body are improved. The gypsum needle crystal that can improve the strength to be comparable to that of polyvinyl chloride resin is a new gypsum needle crystal that has the properties shown below. It has an average diameter of about 1.2 μm or less, and an adsorption amount of water per unit surface area of about 0.3 g/77/m or less, preferably 0.265 g/77/m
■It is a needle-like crystal characterized by a crystalline diameter of less than /d.

The average diameter of gypsum needle crystals must be determined as a macroscopic quantity, so it can be determined from the time at which sedimentation begins.

Here, the sedimentation start time is a value defined by the method described below. 2 g of classified type 1 water gypsum needle crystals were added to 1.00 ml of distilled water and stirred for 5 minutes to disperse well in the water.

Next, the slurry in which the face acicular crystals are dispersed is poured into a 200 m graduated cylinder having a depth of about 161 m and left to stand still.

Eventually, precipitation of gypsum needles occurs. The sedimentation volume of gypsum sword crystals decreases with time, but when the sedimentation volume is about 90 m1 or more, the rate of decrease over time is small, and the sedimentation volume is about 90 m1. When , the rate of decrease in sedimentation volume over time is large. Based on the above phenomenon, the standing time required for the sedimentation volume to decrease to 90- is defined as the sedimentation start time. In addition, the above-mentioned "sedimentation volume" refers to the volume of the slurry portion in which gypsum needle crystals are dispersed, that is, the volume of 10
It means the volume obtained by subtracting the supernatant liquid from 0-, and is not the volume of solid content sedimentation after standing still for a long time, which is generally used.

Now, the sedimentation start time defined as described above is a macroscopic value that depends on the shape of the gypsum needle crystals. According to the research conducted by the present inventors, the settling start time depends only on the diameter of the gypsum needle crystals, and does not depend on the length when the length is 20 μm or more. The smaller the diameter of the gypsum needles, the longer the settling start time. The correspondence between the diameter of gypsum needle crystals and the settling start time can be determined from electron micrographs.

- The average diameter of the volume was determined for several electron micrographs in which hundreds of gypsum needle crystals were dispersed. Sedimentation start time approx. 5
．． 8 minutes corresponds to an average diameter of about 1.2μ determined from electron micrographs.

Gypsum needle crystals having an average diameter of 1.2 μm or less as measured by the above method are the small diameter gypsum needle crystals according to the present invention.

The amount of water adsorbed per unit surface area is measured by the following method. First, the sample is fired at 800°C for 60 minutes. This firing is called pretreatment. The specific surface area of the pretreated (1) type water gypsum needle crystals is measured by the usual BET method using nitrogen. Let that value be A (m/II). Next, calculate the amount of water adsorption, which is the amount of water adsorption when changing the vapor pressure of the system at 20°C. Measure the amount. If this value is B (f/f), the amount of water adsorbed per unit surface area is B/A (f/Wf). The pretreatment conditions are important.

Generally, when α-type aquatic gypsum needle crystals or ■-type aquatic gypsum needle crystals are fired, the BET specific surface area and the adsorption amount of water tend to decrease as the firing is performed at a high temperature for a long time. However, according to the research of the present inventors, if the gypsum needle crystals are fired at an unnecessarily high temperature for a long time, the surface of the gypsum needle crystals becomes as if they were melted, and the surface condition of the gypsum needle crystals changes significantly. Because the width changes, it is unsuitable as a pretreatment for measuring the surface area of gypsum needle crystals. However, after firing at 800°C for 60 minutes, no evidence of melting of the surface of the gypsum needle crystals was observed.

On the other hand, when industrially producing ■-type hydrogypsum needle crystals, α-type medium hydrogypsum needle crystals or ■-type hydrogypsum needle crystals are produced without cutting, and then these gypsum needle crystals are fired. By doing so, ■ type water gypsum needle crystals are obtained. Therefore, the firing temperature is usually 400 to 700°C. The reason is that, firstly, if the firing temperature is lower than 400°C, there is a strong possibility that A-type aqueous gypsum needle crystals or ■-type aqueous gypsum needle crystals will remain unconverted, which is undesirable. . Second, the higher the firing temperature, the higher the energy cost. A temperature of 600 to 700[deg.] C. at which α-type aqueous gypsum needle crystals or ■-type aqueous gypsum needle crystals are converted into -type aqueous gypsum needle crystals is sufficient. Therefore, the firing temperature employed industrially is usually about 700°C or less, and rarely exceeds 800°C. For the above reasons, 800°C for 60 minutes was adopted as the pretreatment condition.

What is important is whether the gypsum needles are α-type mesohydrite gypsum needles, ■ type aquatic gypsum needles, or ■
Even if the gypsum needle crystals are in the form of water gypsum needle crystals (however, when fired at a temperature below 800°C), the reinforcing properties of the gypsum needle crystals for the polyvinyl chloride resin will change after the gypsum needle crystals are pretreated. is defined by the amount of water adsorbed per unit surface area. That is, the effect of the present invention is exhibited when the amount of water adsorbed per unit surface area is 0.3 cm/nt or less, preferably 0.26'5 k/nt or less.

Generally, the breaking (tensile) strength per unit cross-sectional area of inorganic fibers such as sapphire whiskers and glass fibers is diameter-dependent; the smaller the diameter, that is, the cross-sectional area, the more
The breaking strength per unit area increases. According to the research conducted by the present inventors, the above-mentioned tendency was generally recognized also in the case of gypsum needle crystals. That is, in the process of kneading and compounding thermoplastic resin and gypsum needle crystals, the smaller the diameter of the gypsum needle crystals, the less breakage of the gypsum needle crystals, and as a result, the gypsum needles in the composite are The aspect ratio of the gypsum needle crystals becomes larger, and the resin reinforcing properties of the gypsum needle crystals increase. In particular, the diameter of gypsum needle crystals is about 2 to 1 μm.
Below this, the degree of damage to the gypsum needle crystals is significantly reduced. On the other hand, even if the diameters of the gypsum needles are approximately the same, the degree of breakage of the gypsum needles during the process of kneading and compounding the gypsum needles with a thermoplastic resin is not necessarily the same. . In other words, it has been found that the aspect ratio of the gypsum needle crystals in the composite and, as a result, the mechanical strength of the composite differ.

The above general tendency also holds true for polyvinyl chloride resins. That is, the modulus of elasticity and the like can be greatly improved and reinforced by making the gypsum needle crystals a cross-wire fraction. In a composite with a polyvinyl chloride resin, the tensile strength is usually not reinforced more than the paste strength, but if the average diameter is 2 to 1 μm or less, the decrease in strength is reduced. On the other hand, in the case of known gypsum needle crystals, the impact strength is significantly reduced even if the average diameter is about 1.2 μm or less. However, when the gypsum acicular crystals according to the present invention are adopted, not only the elastic modulus etc. are improved and reinforced more than the conventional gypsum acicular crystals, but also the impact strength is equivalent to the base strength. will be realized. That is, the present invention is unique in improving impact strength.

Conventionally, filler dispersibility has been considered to be one of the factors that greatly influences the impact strength of PVC-based composite materials. The better the dispersion of the fibers, the more remarkable the improvement in impact strength.

However, in order to properly disperse conventional gypsum needle crystals in vinyl chloride resin, it is necessary to remove large particles and aggregates, and also to use processing methods that require large shearing force, such as roll kneading. Good dispersion of gypsum needle crystals was difficult to achieve unless the method was adopted. However, in the case of roll kneading, the gypsum acicular crystals are significantly damaged and the aspect ratio of the gypsum ω1-like crystals in the processed molded product becomes small, so that the reinforcement of the mechanical strength of the molded product becomes low. In particular, the decrease in tensile strength becomes significant. Here, there is a difficulty in balancing tensile strength and impact strength. However, since the dispersion of the gypsum needles according to the present invention is better than that of the conventional gypsum swords, the dispersion of the gypsum needles according to the present invention is better than that of the conventional gypsum swords. It is possible to achieve dispersion. Therefore, according to the present invention, the mechanical strength, particularly the impact strength, of the molded article is significantly improved compared to the conventional case. In other words, if the gypsum needle crystals according to the present invention are used, a composite material with both tensile strength and impact strength balanced to the base strength can be produced by powder extrusion, which is a common processing method for polyvinyl chloride resin. It is possible to obtain this. Of course, the rigidity will be greatly improved.

Furthermore, when the gypsum needle crystals according to the present invention are composited with an organic polymer other than polyvinyl chloride resin, such as a polyolefin resin that is a thermoplastic resin, the mechanical strength such as rigidity and tensile strength is lower than that of conventional gypsum. It was found that the reinforcement was significantly greater than in the case of needle-shaped crystals. For example, when a polypropylene resin, which is a typical polyolefin resin, is composited with the gypsum needle crystals of the present invention, the tensile strength is significantly enhanced compared to when a conventional gypsum needle crystal is composited. The strength of rupture of gypsum acicular crystals and the reinforcing properties of the composite with organic polymers depend on the diameter of the acicular crystals on the surface, and even if the diameters are almost the same, the aspect ratio in the composite is It has already been explained that the reinforcing properties are different. The gypsum acicular crystals according to the present invention have significantly higher tensile strength of the composite than conventional gypsum acicular crystals even though the diameters are approximately the same. That is, the present invention is distinctive in dramatically improving the mechanical strength of polyolefin resins.

According to the monofilament reinforcement theory, the tensile strength '1's of a fiber-reinforced composite is expressed by the first equation.

T' S = l / d −x ・τ・V1+am
(1-Vf) --First formula l...Fiber length in the composite. (Lj L l < 1° (critical fiber length) d...Fiber diameter χ...#l! Constant related to fiber orientation τ...Interfacial shear strength between fiber and matrix Vl...Fiber Volume fraction σm... When the strength fibers of the matrix are gypsum needle crystals, 1/d in Equation 81, that is, the aspect ratio, is the average value after breakage in the composite process. The aspect ratio is considered to depend on the toughness of the gypsum needle crystal itself, i.e., jt / docσ.The second equation, where, σ
G can be assumed to be the strength of the gypsum needle crystal itself, for example, the breaking strength. On the other hand, it has been confirmed that the breaking strength of whiskers and glass fibers is diameter dependent, and as the diameter becomes smaller, the breaking strength increases significantly and approaches the theoretical strength. The relationship between the breaking strength and the diameter can be approximated by, for example, an exponential function. Now, assuming that the fracture strength of the gypsum needle crystal, which is a whisker-like crystal, has a diradial dependence, formally, σo oc l'...3 It can be written as expression. Therefore, from the first to third equations above, TS'm(1, Vf) =x-r-Vf-1/dcx
l'-・-.

4th formula % Formula % ... It is thought that the 5th formula holds approximately. The constants a and b are determined by substituting actual measured values for a gypsum sword crystal that is considered to have very few stress concentration points, such as the steps described below. The unit of tensile strength is 9 /
ctl, unit of diameter in micron, lever, a; 0.60
, b; 6.41 f6 le.

According to the research of the present inventors, conventional gypsum needle crystals are
The deviation from the fifth equation, that is, at a certain diameter, the difference between TS calculated from the fifth equation and the actual measurement T8 is large. In particular, the diameter is about 1.
If it is less than 2μ, the deviation becomes very large. On the other hand, if such gypsum needle crystals are used, the diameter will be about 1.
Even if it is 2μ or less, the deviation from the fifth equation is small. Therefore, in the fifth equation, TS for an arbitrary diameter d is defined as the tensile strength T8'(d) of the composite when ideal gypsum needle crystals are adopted, and then Actual measured value of gypsum needle crystal complex T S ((1), T S
Determine the magnitude of the drop from o(d) and calculate it as ΔTS((1
)=TS' (a)-TS(d).

The tensile strength of the gypsum needle crystal composite is determined as follows. After classification, 40 parts by weight of Type 1 water gypsum needle crystals were added and mixed with 54 parts by weight of polypropylene resin powder, 6 parts by weight of acrylic acid-modified polypropylene resin, and a small amount of stabilizer, and 40 parts by weight of uniaxial vent extrusion. (Dulmage screw) machine at about 240°C, and then the dried pellets were pelletized at a mold temperature of 60°C and an injection pressure of about 6°C.
250 JISK-6745 test pieces at 00 kg/cd
Injection molding is carried out at a temperature of about 23° C. and a tensile test is carried out at a pulling rate of 5 mm/min.

On the other hand, the diameter d of the gypsum needle crystals is determined from the sedimentation start time,
The ideal tensile strength T8'(d) at the same diameter is calculated from the fifth equation, and then ΔT8(d)=TS'((1)-T
S (fill in (1).

ΔTS(d) defined as above is considered to be a parameter of toughness of the gypsum needle crystal. That is, gypsum needle crystals with a small ΔT8 are stronger than gypsum needle crystals with a large ΔTS(d).

Strong gypsum needle crystals are gypsum needle crystals that are less likely to break during the kneading and compounding process with resin, in other words, have fewer stress concentration points such as steps and dislocations on the crystal surface. Since the stress concentration point is considered to be an active point on the crystal surface, it is considered that the adsorption capacity for highly polar water molecules is extremely large. In other words, it is thought that gypsum needle crystals with a large ΔT8 ((1)) also have a large adsorption amount of water molecules.In fact, conventional gypsum needle crystals have a large ΔT8((1)) and a large amount of water molecules per unit surface area. In contrast, the gypsum needle crystals according to the present invention have a small ΔTS(d) and a small adsorption amount of water per unit surface area. A clear first-order correlation can be seen between the amount of adsorption and this relationship is shown in FIG.

The amount of water adsorbed per unit surface area of light is 0.8 trry/vf, which corresponds to ΔTS=60, and the amount of water adsorbed per unit surface area of the more preferable gypsum needle crystal is 0.265 mW.
/n? The following corresponds to ΔT8 of 40 kq/c- or less. Therefore, the gypsum needle crystal according to the present invention is practically
It is preferable to specify T8.

Now, the gypsum needle crystal according to the present invention is defined by three items.

The first condition, that the average diameter is about 1.2 μm or less, is considered to be based on the diameter dependence of gypsum needle crystals, as described above. When the diameter is about 1.2 μ or less, the strength of the gypsum needle crystals generally increases significantly, so there is less damage during kneading, and as a result, the aspect ratio of the gypsum needle crystals in the formed product increases. Therefore, it is thought that the tensile strength is improved.

The second condition is that the amount of water adsorbed per unit surface area is approximately 0.
．． Regarding the reason why it is necessary to be 3η/R or less,
It's not clear. However, the fact that the adsorption amount of water per unit surface area is different means that there are places that preferentially adsorb water molecules, which are more polar than nitrogen molecules, and the amount of water molecules that are present in the It can be interpreted that it varies greatly depending on the type of crystal. The adsorption point (field) can be assumed to be, for example, a step or transition on the crystal surface. In other words, it is considered that gypsum needle crystals that adsorb a small amount of water per unit surface area are less likely to break due to fewer steps on the crystal surface. Particularly preferred gypsum needle crystals have an adsorption amount of water per unit surface area of 0.265/
n? It is considered to be a gypsum needle-like crystal with a strength close to ideal, with a particularly small number of steps.

It is common knowledge in mJ that this is expressed as reinforcement for the strength (in other words, a reduction in ΔTS) when combined with PP. On the other hand, as described in rrlJ, when combined with PvC, the strength and impact strength are not significantly reduced.

Furthermore, the number of gypsum needle crystals that meet the above two conditions is about 20.
It is extremely advantageous from the point of view of improving impact strength if it does not substantially contain particles or agglomerates with a size larger than μ. In general, it is thought that when large particles or aggregates are present, they become stress concentration points and cracks easily develop, resulting in a decrease in impact strength. Removal of particulates or agglomerates can be accomplished by classification, such as in a forced vortex two rotating wall classifier. The degree of classification may be determined as appropriate depending on the purpose of use, but it is desirable that the amount of particles or aggregates be at least about 1% by weight or less.

As already explained, the dispersibility of the gypsum needle crystals according to the present invention in polyvinyl chloride resin is significantly better than that of conventional gypsum needle crystals, and one of the reasons for this is that The adsorption point is considered. In other words, conventional gypsum needle crystals have many adsorption points, in other words, active points on the crystal surface, and the gypsum needle crystals themselves have strong cohesiveness.
Since there are very few active sites on the surface of the gypsum needle crystals according to the present invention, it is thought that the gypsum needle crystals themselves have weak cohesiveness and are easily dispersed well. It is believed that the impact strength is significantly improved as a result of good dispersion.

The gypsum needle crystals defined as above can be produced as follows. Raw materials 2 Water gypsum to water 0
．． An aqueous slurry containing 3 to 30% by weight of the slurry is placed in an autoclave and heated under pressure while stirring to produce α-type mesohydrate gypsum needle crystals.

Here, the properties of the raw material dihydrate gypsum must have the following characteristics. That is, the half-value width (during integration after correction) of the X-ray diffraction peak of the (OO2) plane is approximately 2.5Xl.
□-11 radians, particularly preferably 15 x 10-4 radians or less, and the solubility of calcium sulfate after about 10 minutes after being introduced and dispersed in water is about 0.204%, particularly preferably 0. It is necessary that it is 202% or less. X
Line diffraction is done by Rigaku Denki Co., Ltd.! 1liIX X-ray diffraction device (
Cat ff12028) under the following conditions.

'varget; Cu (45KV 40mA)J
・'i 1ter; Ni Divergency; 1/2゜Jjeceiving 51it; Q, 3 shoulders a+5
can 5peed; l/2”/1nChart
Speed; 8θMN/m 'I'ime Qonst; 55ec, half fd
As the standard material for li width correction, α-81(')2 having a particle size of 80 to 44 μ and annealed at 800′C was used.

The solubility of calcium sulfate is determined by its electrical conductivity at 19°C. That is, the electrical conductivity of an aqueous solution of calcium sulfate with a known concentration is measured at 19°C, and a calibration curve is created. Next, the electrical conductivity of the sample to be measured is measured at 19°C, and the solubility of the sample can be estimated from the above calibration curve. The particle size of the raw material 2-water gypsum is several microns.
~100μ, more preferably several μ to 60μ is appropriate.

The fine raw material dihydrate gypsum is obtained, for example, by hydrating calcined gypsum. The baked gypsum used here is
Substantially does not contain dihydrate gypsum or H-type hydrogypsum, and furthermore,
It is preferable to use calcined gypsum, which has a large microcrystalline grain size calculated from the half-width of the X-ray diffraction peak by the formula ())all, and has a small lattice strain of the microcrystals.

The solubility (calcium sulfate equivalent) of fine hydrated dihydrate gypsum obtained by hydrating preferred calcined stone at a concentration of 0.8 to 30% by weight at room temperature with stirring is approximately 1 hour after the start of water use. It is about 0.204% or less, and furthermore, the half width of the X-ray diffraction peak of the (002) plane of the hydrated dihydrate gypsum crystal is about 2.5 X I O-4 radians or less.

In addition to the raw material dihydrate gypsum, it may be possible to obtain favorable results by adding seed crystals. In particular, when the particle size of the raw dihydric gypsum is relatively large, adding seed crystals can increase the diameter of the resulting α-visual gypsum needle crystals by 1
．． If it is thinned to 2μ or less, a hole will be formed. An example of such seed crystals is fine hydrated dihydrate gypsum obtained by hydrating calcined gypsum by the method described above. The calcined gypsum used here is obtained by calcining dihydrate gypsum using a conventional method. Fine hydration 2 obtained by hydrating calcined gypsum whose microcrystalline particle size is smaller than the half width of the X-ray diffraction peak of calcined gypsum and whose lattice strain is large.
Gypsum is highly effective as a seed crystal. That is, a preferable seed crystal can produce small-diameter gypsum needle-like crystals with a relatively small amount of addition. Hydrated dihydrate gypsum, which is highly effective as a seed crystal, has a high solubility. Also, the X of the (OO2) plane
Hydrated dihydrate gypsum, which has a large line diffraction peak half width, is also highly effective as a seed crystal. However, the solubility is 0.204
% or the half width of the X-ray diffraction peak of the (002) plane exceeds 2.5 x 10 = radians, the diameter of the resulting gypsum needle crystals will be Although it becomes thinner, the amount of water adsorbed per unit surface area increases. Conversely, when the amount of seed crystals added is small, the diameter of the obtained gypsum needle crystals becomes thick.

Preferred combinations of the properties and amount of the hydrated dihydrate gypsum to be added are in the water range below. The solubility of fine hydrated dihydrate gypsum (seed crystals) obtained by hydrating calcined gypsum (about 1 hour after the start of water use, 19'C) is 0.204% or less, and the (002 ) If the half width (integral width after correction) of the X-ray diffraction peak of The solubility at 19°C of By adding 3% or more of , the gypsum needle crystals according to the present invention can be produced.

Solubility of fine hydrated gypsum (seed crystals) obtained by hydrating calcined gypsum (19°C after approximately 1 hour from the start of hydration)
exceeds 0.204%, or the hydrated dihydrate gypsum (
The half-width of the X-ray diffraction peak of the (002) plane of the (seed crystal)
When adding hydrated dihydrate gypsum with an integral width (after correction) exceeding 2.5 x 10 radians as a seed crystal, when adding the seed crystal to the above-mentioned raw material dihydrate gypsum, Seed crystals (fine hydration obtained by hydrating baked stone 2)
Water gypsum) solubility (about 1 hour after the start of water use, 19°
When C) is X percent and 2 is the amount (percent) of the seed crystal added, in the (X, Z) coordinates, it is a combination within the range shown by the shaded area in FIG. When the half width (integral width after correction) of the X-ray diffraction peak of the (002) plane is set as Y radian, the combination of the range shown by the shaded area in Figure 2 in the (Y, Z) coordinates is By starting from a satisfactory mixture it is possible to produce the gypsum needles according to the invention.

Now, the solubility of gypsum is considered to depend on the particle size and surface crystallinity of the gypsum. Therefore, it is possible to reduce the solubility of the gypsum by washing the gypsum with water or leaving it to mature after being dispersed in water. However, solubility is determined by a very small amount of very fine particles or lattice defects on the crystal surface, so even if the solubility decreases significantly, the inside of the gypsum crystal It is inconceivable that there has been a drastic change to the (non-surface) state.

On the other hand, the half width of the X-ray diffraction peak is a quantity that depends on the crystal grain size in the direction perpendicular to the crystal plane of interest and the average value of lattice strain in the direction perpendicular to the crystal plane. Dihydrate gypsum obtained by hydrating calcined gypsum by the above-described method generally becomes rod-shaped crystals extending in the C-axis direction. However, since the (002) plane of dihydrate gypsum is perpendicular to the C axis, (002)
The half width of the surface X-ray diffraction peak depends on the size of the dihydrate gypsum in the elongation axis direction and the average value of lattice strain.

Since the fine rod-shaped crystals of hydrated gypsum are considered to be single crystals, the size in the C-axis direction is several to several tens of microns, and their contribution to the half-value width is so small that it can be almost ignored. The half width of the X-ray diffraction peak of the (002) plane of hydrated dihydrate gypsum is equal to the average lattice strain in the C-axis direction, including the surface and interior of the dihydrate gypsum.

It is considered to be a parameter indicating the size.

According to the research conducted by the present inventors, hydration 2 with relatively high solubility
The half value 1 of the X-ray diffraction peak of the (002) plane of hydrated dihydrate gypsum, whose solubility has been greatly reduced by aging the hydrogypsum, is compared to the half value before aging. Although there is a slight decrease in solubility, it is much smaller than the rate of decrease in solubility.The above phenomenon is due to the fact that solubility depends on the grain size and surface condition of gypsum, and the half-width of the X-ray diffraction peak This is considered to be evidence that the quantity represents the average crystal state of the entire crystal. The production of gypsum needle crystals is carried out under dynamic equilibrium conditions in which dihydrate gypsum is dissolved in water and crystallized as α-type gypsum.

As the dissolution of dihydrate gypsum progresses, the interior of the dihydrate gypsum crystal becomes a new surface layer, so the solubility of the system depends on the properties of the new surface layer, that is, the properties of the original interior of the dihydrate gypsum crystal, in other words. , is considered to be defined by the half width of the X-ray diffraction peak. This is considered to be the importance of measuring the half width of the X-ray diffraction peak.

However, reducing solubility is beneficial. In the crystallization of α-type gypsum, the difference between the solubility of dihydrate gypsum and the solubility of α-type gypsum is considered to be the degree of supersaturation, so if the solubility of dihydrate gypsum is lowered, It is thought that the degree of supersaturation is reduced accordingly, and gradual crystallization is realized. In general, crystals with few impurities, lattice defects, or steps are achieved by keeping the degree of supersaturation low and achieving a slow crystallization rate.

α-type earth water gypsum needle crystals are substantially 115° to 13
Manufactured at 0°C. It is preferable to stir the slurry at a low speed within a range that prevents sedimentation of the solid content of the slurry. When the stirring speed is low, the diameter of the obtained gypsum needles can be made smaller.

The produced α-type clay gypsum needle crystals are dehydrated and separated, dried, and then calcined at 400 to 700°C to obtain stable ■-type clay gypsum needle crystals.

The ratio of adding gypsum needle crystals to the synthetic resin is 5 to 75%.
Weight % is appropriate. When the content is less than 5%, there is little advantage in adding gypsum needle crystals to the composite, and it is often difficult to create a composite when the content exceeds 75%.

Next, examples will be described.

Example 1 By calcining the flue gas desulfurization by-product dihydrate gypsum at 180°C for 16 hours, the microcrystalline particle size was approximately 0.125 microns.
Calcined gypsum with a microcrystalline lattice strain of approximately 1.4 x 10" was obtained. The calcined gypsum was then hydrated. The solubility of calcium sulfate immediately before use, approximately 1 hour after the start of water use, was 0.
．． The half width of the X-ray diffraction peak of the 202% (002) plane was approximately 1.45×10′ radian. The hydrated dihydrate gypsum slurry having a slurry concentration of about 5% by weight was placed in an externally heated autoclave and heated under pressure while stirring. The slurry temperature was raised to about 130°C and held for 5 minutes to complete the reaction.

After cooling the internal temperature to about 90°C, it was quickly dehydrated and separated to obtain a dehydrated cake of σ-visual water gypsum needle crystals. Next, the dehydrated cake was placed in a hot air calcining furnace (C) at about 700°C and dried and calcined for about 30 minutes to obtain type 1 water gypsum needle crystals. Particulate matter and aggregates of about 20μ or more were removed using a classifier) to obtain type 1 water gypsum needle crystals with an average diameter of about 0.79μ.After classification, the 2 type water gypsum needle crystals were
After baking (pretreatment) at 00°C for 60 minutes, the amount of water adsorbed per unit surface area was measured. The results are shown in Table 1.

1001), and a belt-like strand was extruded using a 40 MM single-screw vent extruder.

Then preheat at 175℃ for 5 minutes, 50kg/ctA
A specimen with a thickness of approximately 3 MII was prepared by pressing for 5 minutes under high pressure, and the specimen weighed 30 mm in a constant temperature room at a temperature of approximately 23°C.
The DuPont impact strength (height at break, cm) was measured using a weight of 0 g and a weight of 3/8 inch percussion. The results are shown in Table 1.

In addition, a tensile test piece was cut out from the above belt technique strand.
A tensile test was conducted according to ISK-6745. The results are shown in Table 1. On the other hand, 20% by weight of the classified ■-shaped anhydrous gypsum needle crystals were added to the lead-containing PVC and pelletized using a 40M vent extruder, and then a belt-like strand was extruded using the same extruder. A tensile test piece was cut out from the belt-like strand and subjected to a tensile test in accordance with JISK-6745. The results are shown in Table 1.

After the above classification, the ■ type water gypsum needle crystals were mixed with 54 parts by weight of polypropylene resin (PP), acrylic acid modified P, and P6.
40 parts by weight were added to each part by weight and some amount of stabilizer, and the pellets were pelletized using a single-screw vent extruder.Then, the dried pellets were molded using a conventional method using an injection molding machine.
IS K-6745 specimens were prepared and tensile tests were conducted at a temperature of approximately 23°C. The results are shown in Table 1.

Comparative Example 1 Flue gas desulfurization by-product dihydrate gypsum, which is different from Example 1, was heated at 220°
By calcining for 4 hours at C, the microcrystalline particle diameter is 0.1
Calcined gypsum with a lattice strain of about 1°8×I O-8 in a 5μ crystal was obtained. The calcined gypsum was then hydrated.

About 1 hour after the start of water use, the solubility of calcium sulfate immediately before use was about 0.207%, and the half width of the X-ray diffraction peak of the (002) plane was about 3.9X], 0' radian. below,
By the same method as in Example 1, a thickness of about 0.65 μm was obtained.
After classification, anhydrous gypsum needle crystals were obtained. Next, the amount of water adsorbed per unit surface area was measured in exactly the same manner as in Example 1, and various physical properties of the composite with PVC and PP were also measured. The results are shown in Table 1.

Comparative Example 2 The microcrystalline particle size of air-flow calcined calcined gypsum is approximately 0.06μ,
The lattice strain of the microcrystal was approximately 8.2×10 −8 .

The solubility of dihydrate gypsum obtained by hydrating this calcined gypsum is approximately 0.235% immediately before use, and the half-value width of the X-ray diffraction peak of the (002) plane is approximately 5.8 x 10-4 radians. there were. Hereinafter, the same method as in Example 1 was used to obtain a thickness of about 0.
An anhydrous gypsum acicular surface was obtained after classification of 59 μm. Next, the amount of water adsorbed per unit surface area and various physical properties of the composite with PVC and PP were measured in exactly the same manner as in Example 1.

The results are shown in Table 1.

Comparative Example 3 Flue gas desulfurization by-product dihydrate gypsum with a particle size of IO ~ 60μ was poured into water and stirred, and the solubility after about 10 minutes was about 0.200.
%, the half width of the X-ray diffraction peak of the (002) plane is approximately i, 1
x1 o' radians. About 1.5% by weight of the hydrated dihydrate gypsum used in Comparative Example 1 was added to the raw material dihydrate gypsum.
Using the added slurry, classified anhydrous gypsum needle crystals having a thickness of approximately 1.5 μm were obtained in the same manner as in Example 1. Next, the amount of adsorption per unit surface area and various physical properties of the composite with PVC and PP were measured in exactly the same manner as in Example 1. The results are shown in Table 1.

Example 2 To the raw dihydrate gypsum used in Comparative Example 3, about 5% by weight of the hydrated dihydrate gypsum used in Comparative Example 2 was added. Thereafter, in the same manner as in Example 1, classified anhydrous gypsum needle crystals having a thickness of approximately 0.83 μm were obtained. Next, the amount of water adsorbed per unit surface area and various physical properties of the composite with PVC and PP were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 3 The hydrated dihydrate gypsum slurry used in Example 1 was dehydrated and separated, washed with water, and dispersed in water again. Solubility is about 0199
%, the half width of the X-ray diffraction peak of the (0'02) plane is approximately 1.
It was 4XlO' radians.

Hereinafter, by the same method as in Example 1, a thickness of about 0.77 μm was obtained.
Classified anhydrous gypsum needle crystals were obtained.

Next, the amount of water adsorbed per unit surface area and various physical properties of the composite with P VO and PP were measured in exactly the same manner as in Example 1. The results are shown in Table 1.

Example 4 To the raw dihydrate gypsum used in Comparative Example 3, 15% by weight of the fine hydrated dihydrate gypsum used in Example 1 was added.

Hereinafter, by the same method as in Example 1, a thickness of about 0.93
Anhydrous gypsum needle crystals classified by μ were obtained. Next, by the same method as in Example 1, the amount of water adsorbed per unit surface area and various physical properties of the composite with PVC and PP were measured. The results are shown in Table 1.

(Panel margin) 44. Brief explanation of the drawings Figures 1 and 2 show the combination ranges of (solubility) - (addition amount) and (half-width) - (addition amount) of hydrated dihydrate gypsum, respectively. The graph shown in Figure 3 shows the graph of gypsum needle crystals.
The adsorption amount of water per unit surface area and the surface acicular crystals are P
Graphs 4 and 5 showing the relationship between ΔTS when compounded with P are (solubility) - (addition amount) and (half-width) of hydrated dihydrate gypsum in Examples and Comparative Examples, respectively. ) - (addition amount) is a graph showing the combination.

A...Example 1, B...Comparative example 11C...Comparative example 2, D...Comparative example 3, E...Example 2, F.
...Example 3, G...Example 4゜Patent applicant Kanebuchi Chemical Industry Co., Ltd. agent Patent attorney Makoto Asano - Mizuji-λ Mizu Stone Kouno'i'('l) Water 4027, ! ;Kou Ck wide amount and Z)≠-Chip2 spear Q ni U no Tame outside-addition f (2,)! Two ~

Claims (5)

[Claims] (1) A composite composition obtained by mixing gypsum needle crystals with a synthetic resin having an average diameter of about 1.2μ or less and an adsorption amount of water per unit surface area of about 0.811Ig/7. . (2) The composite composition according to claim 1, which does not substantially contain particles or aggregates of about 20 microns or more in plaster. (3) The composite composition according to claim 1 or 2, wherein the amount of gypsum needle crystals mixed into the synthetic resin is 5 to 75% by weight based on the synthetic resin. (4) The composite composition according to claim 1 or 2, wherein the synthetic resin is a polyvinyl chloride resin. (5) The composite composition according to claim 1 or 2, wherein the synthetic resin is a polyolefin resin.