JP2003041151A - Method for colored silica sand production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inexpensively producing colored silica sand to be hardly ground finely and to hardly wear out an artificial lawn pile, with which a thick colored coating film can be formed without requiring a complicated process. SOLUTION: This method for colored silica sand production has a process for mixing 100 parts.wt. of silica sand having 0.5-1.5 mm particle diameter with a film-forming material comprising 5-60 parts.wt. of one-pack type or two-pack type polyurethane resin which is at least gelled from a liquid state in >=120 seconds and cured through the process and pigment with stirring and continuing the mixing with stirring even after the gelation of the polyurethane resin and starting of agglomeration of rubber chips so as to release the agglomeration of the silica sand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing colored silica sand which can be suitably used as filler sand (soil) for artificial grass containing sand. More specifically, the present invention relates to a flexible thick film coloring film around silica sand. To a method of forming.

[0002]

2. Description of the Related Art Artificial turf containing sand with artificial sand filled with silica sand has excellent cushioning properties, excellent sliding performance without sudden braking, and has been widely used in recent years to reduce the burden on the feet. However, the following drawbacks are a problem.

1) Particles are broken and crushed by friction between silica sand due to load such as movement and impact, and solidified by moisture such as rain, so-called cementation phenomenon occurs and shock absorption,
It is dangerous because it loses cushioning and becomes hard.

2) Silica sand is crushed, and small particles and powder are scattered around and become a pollution source.

3) Since silica sand rubs against the artificial turf pile due to a load or impact such as exercise, the artificial turf pile is easily worn away, and eventually wears out and is not torn off, resulting in an extreme appearance. become worse.

4) The above-mentioned phenomena 1) to 3) occur in about 5 years in a part where the frequency of use is high, for example, near the baseline of a tennis court, and the short life is a major drawback. Also, replacing the sand costs a lot of money,
Since artificial turf cannot be partially repaired, not only is it necessary to cut and repair a considerably large area, but the cut artificial turf becomes industrial waste, which increases repair costs.

5) Many methods have been proposed for mixing elastic materials such as rubber powder and rubber chips into sand. However, in Japan, there is a lot of rainfall, and during heavy rainfall, the elastic material flows out and is discharged to the outside to protect the environment. There is a risk of contamination.

6) Since the silica sand is a light beige color, the artificial turf is faint in color and a white line is drawn.
The line is hard to see.

As means for solving such problems, various methods have been proposed in which the surface of silica sand or the like is coated with rubber or plastic.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 1-131705, as a sand to be filled in a lower layer for a sand-containing artificial grass, a solvent of a butadiene-based synthetic rubber, a polyolefin-based body, an elastic body such as polyurethane, or a solution is sprayed, Although coating by dipping is described, the publication only describes that "elastic particles obtained by coating silica sand to 0.5 mm with silica having a particle diameter of 0.5 to 1.0 mm" in Examples. However, no specific coating technique is described.

Further, in JP-A-6-15065 and JP-A-6-235206, components made of a synthetic resin such as silicone type, polyurethane type, vinyl acetate type and / or oil such as silicone oil are mixed with a mixer. After mixing, it is left for a long time and a method for producing filled sand for artificial grass containing sand is described.

However, these publications do not specify the amount of resin used in the coating, and in the examples, silica sand 4 is used.
8 parts of polyurethane resin emulsion in 00 parts (solid content 5
Even if it is 0%, it is substantially 4 parts), and the colored film is very thin, and the coating thickness is extremely high in order to improve the fatal defects of silica sand such as suppressing the cementation phenomenon and suppressing the abrasion of the artificial grass pile. It is very thin. Further, since an emulsion is used, a drying process is required, the process is complicated and expensive, and a large amount of non-reactive oil is contained, so there is a concern that it may be discharged into the environment.

Further, Japanese Patent Application Laid-Open No. 61-103417 discloses a method of spraying and coating a solution of a material to be coated while dropping sand until it falls to the bottom.

However, in such a method, since the probability that the spray droplets collide with the falling particles is low, the loss amount of the material is large compared to the adhered amount, which is very uneconomical, and the collision place is limited. It is not applied to and the thickness is uneven.
It is unlikely that the bias can be resolved by doing this several times,
Even if it is dried while falling, it is not realistic because the particles do not dry sufficiently and aggregate with each other. Further, the use of an organic solvent is dangerous at the time of heating and drying, and this amount causes a loss, resulting in an increase in cost.

[0015]

In view of the above-mentioned problems of the prior art, the present invention makes it possible to inexpensively produce colored silica sand which can form a thick colored film without requiring complicated steps, is hard to be pulverized, and is hard to wear off an artificial grass pile. An object is to provide a production method that can be obtained.

[0016]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have surprisingly found that a large amount of polyurethane resin is used so that silica sand aggregates in order to form a thick film. Also, they found that the agglomeration can be released by continuing stirring and mixing even after the gelation of the polyurethane resin starts and the silica sand begins to agglomerate, and the present invention has been completed.

That is, according to the method for producing colored silica sand of the present invention, 100 parts by weight of silica sand having a particle diameter of 0.5 to 1.5 mm is gelled in at least 120 seconds from a liquid state, and is cured through this process. Or two-component polyurethane resin 5-60
A step of adding a part by weight and a film-forming material containing a pigment and stirring and mixing, and continuing stirring and mixing even after the silica gel starts to agglomerate and the silica sand begins to agglomerate to release the agglomeration of the silica sand It is characterized by having.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

In the present invention, when silica sand and a film-forming material containing a polyurethane resin, a pigment and other fillers are added and mixed with stirring, the viscosity of the mixture is low at first, but it is in a fluid state but reacts with moisture in the air. The viscosity increases as it progresses, making it difficult to flow, gradually gelling, the resin becomes a jelly, and the whole begins to agglomerate into a large group, barely flowing. If you continue mixing, it will gradually decompose into several medium-sized groups, and then the stickiness will decrease, and finally the silica sand will be decomposed and separated into simple substances, and will be loosened into pieces. The rotation is stopped to obtain silica sand having a colored film.

Since the silica sand repeats separation and dispersion to dissolve the agglomeration in a short time and to stop stirring, the film on the silica sand surface is relatively uniform.

If stirring is continued after this, the coating on the surface of the silica sand will be scraped off and the uniformity of the coating thickness will be impaired. Therefore, excessive stirring is not preferable.

Due to the progress of the cross-linking reaction from the liquid state of the polyurethane resin until it finally becomes an elastic body, a fluid liquid → an increase in viscosity → a gelled state with a little fluidity but a strong consistency (jelly). State) → gelling state of little viscous property with little fluidity → dry state by touch → apparent curing → final curing state through the process of elastic body. If pigment is added to silica sand and urethane resin, which is a film-forming resin, and mixing is continued, the viscosity increases, and eventually gelation begins and the resin becomes jelly-like, and the whole begins to agglomerate and agglomerates into a large group. However, if the stirring is continued forcibly, the jelly shape gradually shifts to a brittle state with less viscosity, and the particles start to separate from each other due to the weight of the particles, and all particles Separates into a simple substance. That is, stirring is forced at the stage of "a gelled state with a little fluidity but a strong consistency (jelly-like)", and a stage of "a weakly gelled state with little fluidity" is reached. It is a great feature of the present invention that it can be separated into a single body by its own weight.

When the particles are separated from each other, the particles may separate or separate the coating films from each other, and at a certain point of time due to the progress of curing, the particles become independent, and the rotation of the mixer is quickly stopped. Is considered to be obtained.

A change in the coating film was confirmed by experiments. That is, in an environment of 25 ° C x 50% RH, polyurethane resin ("Surfam F-9", manufactured by Yokohama Rubber Co., Ltd., quick-curing type 1-liquid moisture-curing urethane prepolymer)
1 wt% of a curing accelerating catalyst (“DABCO 33LV”, a tertiary amine catalyst manufactured by Air Products Co., Ltd.) was added and uniformly stirred, and then applied on a stainless steel plate to a thickness of 0.8 mm to change the state over time. It was as shown in Table 1 when observed later.

[0025]

[Table 1]

From Table 1, it can be seen that in step E, the whole aggregates into a large aggregate, and while mixing is still continued, the aggregate becomes smaller in step F, and eventually the aggregates are separated even to the individual particles. It will be canceled. Therefore, the shorter the time from step F to G, the more uniform the thickness of the film obtained. The particles do not stick together at all and do not aggregate again, but a small amount of powder may be sprinkled as a precaution. The strength of the coated film rises sharply, and the film is no longer scraped or torn off.

Further, as described later, the case where the inorganic or organic powder is added at the time when the gelling of the polyurethane resin starts and the silica sand starts to agglomerate was also considered. If an inorganic or organic powder is added at the start of gelation,
There is an advantage that the agglomeration can be released earlier without burdening the mixer before the whole becomes a very viscous agglomeration state.

From Table 1, when an organic or inorganic powder is added during steps D to E, the powder is kneaded into the urethane resin film at first, and when it becomes a hard gel state, it is formed in the film. It becomes difficult to enter, and the surface is covered with dust. At this point, the aggregation of particles, which tended to be agglomerated, suddenly fell apart, the particles themselves did not stick together at all, and did not agglomerate again. The strength of the coated film rises rapidly, and the film is no longer scraped or torn off.

Even if the powder is added before the step D, the agglomeration cannot be released unless the powder is added until the time when the step E is exceeded, and the powder enters the film too much and the physical properties of the film are fragile. It is not preferable.

The silica sand used in the present invention includes natural sand such as river sand and sea sand, as well as sand generated when rocks are crushed and inorganic particles such as glass and ceramics having a particle size of 0.5 to 1.5.
mm can be used.

As the one-part or two-part polyurethane resin, any binder or urethane polymer conventionally used in rubber chip elastic pavement materials may be used as long as it gels from a liquid state in 120 seconds or more and hardens through this process. Elastomer resins can be used.

The time until gelation is 120 seconds or more within the range where the film can be formed. When it is shorter than 120 seconds, the time from aggregation to curing is too short and a part remains in an aggregated state in the form of dumplings. However, the yield at which the aggregation can be released decreases, and the productivity deteriorates. In addition, if the polyurethane resin takes too long to gel, the gelled and unstable intermediate state is also long, so there is a risk that the silica sand will be aggregated again if the mixer is stopped after it is loosened. However, the treatment time becomes long, the coating is scraped, the coating thickness is reduced, and the uniformity of the thickness may be impaired. Therefore, the time until proper gelation is preferably within 60 minutes, more preferably 10-6.
0 minutes. If it is out of this range, it may be adjusted by heating, cooling, adjusting the amount of catalyst, adding water or the like.

Examples of the one-component polyurethane resin include moisture-curable urethane prepolymers such as polypropylene glycol, polytetramethylene glycol, polybutadiene polyol, etc. in excess of toluene diisocyanate, diphenylmethane diisocyanate,
A urethane prepolymer which is liquid at room temperature and is obtained by reacting an isocyanate such as polymethylene polyphenyl isocyanate or hexamethylene diisocyanate or a modified isocyanate thereof such as a urethane modified product or a carbodiimide modified product, and having an isocyanate group content of 3 to
It is 15%.

In order to accelerate the curing, it is preferable to use a tertiary amine such as trimethylamine, triethylamine or N-methylmorpholine, or an organic metal salt such as lead or tin as a catalyst. Further, diamines which are isocyanate group curing agents such as o-dichlorodiaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 1,3- and 1,4-phenylenediamine, 2,4- and 2,6-
You may add diaminotoluene etc.

Further, as will be described later, when spraying water in a mist before gelation to promote gelation, water reacts with an isocyanate group. Instead of this reaction, for example, an oxazolidine ring is used. A latent curing agent having is added to the binder in advance, and when sprayed with water, it reacts with water to open the oxazolidine ring and the amine and alcohol groups react with the isocyanate group, leading to gelation and curing. You can also do it.

As the two-component polyurethane resin, for example, the above-mentioned one-component urethane prepolymer is used as a main component, and a polyol such as polyether polyol or polybutadiene polyol and the above diamines are used alone or in a mixture as a curing agent. used. It is preferable to use an organic metal salt such as lead or tin as a catalyst in order to accelerate the curing. However, as will be described later, when spraying mist-like water before gelation in order to promote gelation, the isocyanate group reacts partly, so the curing agent should be set to a small amount.

The polyurethane resin is used in an amount of 5 to 60 parts by weight, preferably 15 to 40 parts by weight, based on 100 parts by weight of silica sand. It is necessary to consider the amount of resin because the surface area is different when the particle size is different (a large particle size requires a small amount of resin, and a small particle size requires a large amount of resin), but the required film thickness In order to obtain the above, the above range is preferable.

If the amount of resin is less than the lower limit, the thickness of the coating becomes thin, and the colored coating is worn out at a relatively early stage due to abrasion, and a sufficient effect cannot be obtained. Further, when the resin amount exceeds the upper limit, it is difficult to release and separate the aggregated state from the aggregated state at the time of production, and some that cannot be partially separated remain,
The yield becomes extremely poor and it becomes difficult to set the manufacturing conditions.
In addition, not all the resin forms a film, which is scraped by the blades of a mixer or the like, and the thickness of the film decreases, and the thickness becomes uneven.

The pigment varies depending on the color. For example, in the case of brick color, brown or yellow, iron oxide, in the case of green, chromium oxide, phthalocyanine organic pigments, in the case of black, carbon black, white. In this case, titanium oxide is used, and various colors can be prepared by combining other pigments.

If necessary, the film-forming material of the present invention may contain other compounding agents.

For example, in order to further improve weather resistance, ozone resistance, water resistance and heat resistance, Irganox 1010 is used.
Antiaging agents such as a phenolic UV absorber (manufactured by Ciba Geigy), Yoshinox BHT (manufactured by Yoshitomi Pharmaceutical Co., Ltd.), a benzotriazole type such as TINUVIN P-327, a benzophenone type UV absorber such as Tomisorp 800, and the like can be added.

Further, depending on the use, it is possible to suppress the generation of bacteria and fungi by previously dispersing them in an appropriate plasticizer and adding an antibacterial and antifungal agent such as zinc pyrithione and zinc 2-pyridinethiol-1 oxide. .

Further, when the agglomeration is released, it is preferable to add an inorganic or organic powder to eliminate the adhesion between the separated silica sands and to prevent the agglomeration even if the stirring and mixing are stopped.

Further, at the time when the gelling of the polyurethane resin begins and the silica sand begins to agglomerate, that is, the viscosity increases due to the progress of the reaction, and at some point the silica sand begins to agglomerate with gelation. Inorganic or organic powder may be added at a relatively early stage of forming a dumpling (when starting to form a dumpling). If the organic or inorganic powder is started to be added and is gradually added, the silica sand, which has been agglomerating within a few tens of seconds, suddenly becomes loose and loose.

However, in this case, unless careful consideration is given to the stirring efficiency and stirring speed of the mixer in accordance with the production amount per batch (batch size), it is difficult to release the agglomeration and the yield may drop. .

The organic or inorganic powder has few factors to reinforce the physical properties, and its main purpose is to prevent sticking and to eliminate the agglomeration of silica sand. Therefore, it is preferable that the cost is as low as possible. Examples of the body include rubber and plastic powders, and examples of the inorganic powder include inorganic powders such as calcium carbonate, talc, silica, clay and kaolin powders, which are usually filled with rubber and plastics. Examples include materials used as materials. The particle size of the organic or inorganic powder is preferably 0.5 to 50 μm.

Further, it is preferable to spray mist-like water before gelling the polyurethane resin. By spraying a small amount of mist-like water before gelation, the time until gelation and the time from gelation to apparent hardening can be greatly shortened, so a little stirring time after releasing the agglomeration of silica sand In the meantime, it is possible to obtain a thicker and more uniform coating because particles are less likely to be rubbed or dented or scraped due to contact with the blades of the mixer. To be

A small amount of water spray is sufficient to promote gelation of the polyurethane resin. Specifically, about 30 to 40% of the equivalent amount is sufficient, and if it is too large, foaming inside the film, a need for a drying step for removing excess water, and the like are not preferable. Therefore, for a prepolymer having an NCO content of 10%, an appropriate amount is 7 g to 9 g per 1 kg. The smaller the size of the fog, the larger the contact area with the polyurethane resin, which is preferable.

The mixer which can be used in the present invention is preferably equipped with a stirring blade and a scraper for scraping off the adhered substances on the bottom and wall surfaces of the container. The rotation speed of the stirring blade is
It is preferable that the speed is low enough not to scrape or peel off the uncured film around the silica sand.

Further, it is preferable that the upper part of the stirring container is opened so that the gelled state can be visually confirmed, and water can be sprayed and organic or inorganic powder can be added. Further, it is preferable that steam or warm water can be passed around the container to heat it so that the curing time (gelation time) can be adjusted.

[0051]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, "part" in an Example means a "weight part."

(Materials used) Silica sand: No. 5 silica sand, 20-70 mesh, Rokujiya Kogyo Co., Ltd., particle size of about 1 mm Polyurethane resin: "Surfam F-9", Yokohama Rubber Co., Ltd., fast curing type One-component moisture-curable urethane prepolymer curing acceleration catalyst: "DABCO33LV", manufactured by Air Products Co., Ltd., tertiary amine catalyst pigment: chromium oxide, manufactured by Nippon Kagaku Kogyo Co., Ltd., inorganic powder: calcium carbonate powder, calcium Maruo (stock)
Made, light calcium carbonate, particle size 0.5μm Urethane emulsion: "Superflex 75
0 ", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., anionic, solid content 40
% Artificial grass: Artificial grass type with sand for tennis court, polypropylene pile length 19mm, manufactured by Senshu Rug Co., Ltd.

<Example 1> 400 parts of No. 5 silica sand was placed in a stirring vessel, 60 parts of a polyurethane resin premixed with 1% of a catalyst and 6 parts of a pigment were added while rotating a stirring blade.
After about 15 minutes at room temperature, the polyurethane resin gradually thickens and begins to gel, and the whole begins to aggregate.
Add 5 parts little by little. The No. 5 silica sand particles are scattered,
Stop the stirring after confirming that the silica sand is separated.

Silica sand having a urethane rubber coating uniformly colored green was obtained.

<Comparative Example 1> 400 parts of No. 5 silica sand was placed in a stirring vessel, 8 parts of urethane emulsion and 5 parts of pigment were added while rotating the stirring blade, and mixed for 15 minutes to remove a little water to remove silica sand. Although the whole was in a free-flowing state without coagulating with the emulsion, 20 parts of the inorganic powder was added, the mixture was further mixed for 5 minutes, and the stirring was stopped. This was placed in an oven at 80 degrees and dried for 4 hours.

The original dough of No. 5 silica sand appeared light in color, and silica sand colored with a slight variation in green was obtained.

(Evaluation Method) The characteristics of the silica sands of Example 1 and Comparative Example 1 were evaluated by the following methods. Also, in addition,
The same evaluation was performed on silica sand not having a colored film formed thereon.

(1) Silica impact crushing test A silica sand impact crushing test was conducted using the tester shown in FIG.
The results are shown in Table 2.

That is, silica sand 2 was put into a cylindrical container 1 having a diameter of 110 mm so as to have a thickness of 2 cm, and a drop load of 1.5 kg, a drop height of 20 cm, and a drop bottom surface φ = 6.5.
cm steel plate 3 with a thickness of 3 mm and a rubber plate 4 of hardness 60
The sample to which was attached was impacted by free fall at 50 cycles for 1 minute for 6 hours, and the particle size distribution before and after the test was measured.

The particle size distribution is determined by sieving a sample into each particle size, weighing each particle size, and measuring the weight with respect to the total mass of the sample.
Displayed in.

Further, the numerical value of the percentage of the particle size overlapping within the same particle size before and after the test is shown as the residual rate for each particle size.

[0062]

[Table 2]

From Table 2, the total residual ratio (the sum of the ratios remaining in each particle size range before the test and after the test) was 11 in Comparative Example 1 of the emulsion-coated silica sand as compared with No. 5 silica sand. In contrast to the improvement in points, in Example 1, the improvement was 51 points compared to No. 5 silica sand, and most of them remained in the original grain size range.

In Example 1, the residual ratio on the large particle size side is high, and the ratio of particles remaining on the particle size of 0.5 mm or more is 88%, which is very excellent. Conversely, No. 5 silica sand is 50%
The above is crushed into a very fine powder of 0.3 mm or less, which results in weakness to impact.

(2) Artificial lawn abrasion test Using the tester shown in FIG. 1, an artificial lawn abrasion test was conducted.
The results are shown in Table 3.

That is, an artificial turf having a pile length of 19 mm, the back side of which is fixed with a double-sided adhesive, is laid in a cylindrical container 1, and silica sand 2 is put on the artificial turf so as to cover most of the grass, and the same conditions as the silica sand crushing test are conducted. After 16 hours of impact, the pile thickness before and after the test was measured. During the test, silica sand was replenished as appropriate so that the silica sand was filled so that the grass was almost hidden.

The pile thickness was measured by pulling out 10 piles at the impacted portion, washing with water to wash the adhering powder, and drying, and measuring with a dial gauge to adopt the thinnest thickness. The average value of the books was calculated. The initial thickness of the pile of artificial turf was 78 μm in the same measurement.

[0068]

[Table 3]

From Table 3, it can be seen that when the colored silica sand of Example 1 was filled, the change in pile thickness was less than when the colored silica sand of No. 5 and the colored silica sand of Comparative Example 1 were filled, and it was worn away by friction with the silica sand. It is difficult to see, and it can be seen that the wear resistance of the artificial grass can be significantly improved.

[0070]

As described above, according to the present invention, even if a mixer having a little inferior stirring efficiency is used for releasing the agglomeration, the releasing efficiency is very good and a coating having a uniform thickness can be obtained. Moreover, since the polyurethane resin used for coating is 100% solids and contains no organic solvent, there is no problem in the process even if it is heated, and since it does not contain water, there is no need to dry it in a separate process. Since it is simple and can be done in a short time, the manufacturing cost is very low.

The colored silica sand obtained by the present invention is
It has the following features, tennis courts, soccer, baseball, other ball fields, golf courses, hockey fields, racetracks,
It can be suitably used as a filler sand for artificial grass containing sand such as school grounds.

1) The elastic film absorbs impact, becomes extremely difficult to be crushed, and does not easily cause a hardening phenomenon, so that the elastic state can be maintained for a long period of time and is unlikely to be a pollution source.

2) The artificial turf pile does not directly rub against hard silica sand but rubs against the elastic film, so that the pile is not damaged and the appearance is maintained for a long time. Is also difficult to change.

3) Since the specific gravity is not much different from that of sand, it rarely flows out due to rain.

4) The life of artificial sand containing sand can be extended.

5) When silica sand is colored green, the color of the artificial grass becomes vivid and the visibility of the line is excellent.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a testing machine used in Examples.

[Explanation of symbols]

1 cylindrical container 2 silica sand 3 iron disk 4 rubber plate

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Claims (4)

[Claims] 1. A one-part or two-part polyurethane resin 5 to 60 which is solidified in 100 parts by weight of silica sand having a particle diameter of 0.5 to 1.5 mm from at least a liquid to 120 seconds or more and hardens through this process. A step of adding a part by weight and a film-forming material containing a pigment and stirring and mixing, and continuing stirring and mixing even after the gelation of the polyurethane resin starts and the rubber chips start to agglomerate to release the agglomeration of the silica sand. A method for producing colored silica sand, which comprises: 2. The method for producing colored silica according to claim 1, wherein an inorganic or organic powder is added at the time when the aggregation is released. 3. The method for producing colored silica sand according to claim 1, wherein an inorganic or organic powder is added at the time when the gelling of the polyurethane resin begins and the silica sand begins to agglomerate. 4. The method for producing colored silica sand according to claim 1, wherein atomized water is sprayed before the gelation.