JPS6364459B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for producing a dropless synthetic resin by applying a dropless coating agent to a synthetic resin molded article such as a synthetic resin film, sheet, or plate. In addition,
In this specification, "dropless" refers to the property that water does not adhere to the surface of a synthetic resin molded product in the form of drops,
"Drop-free agent" refers to a drug that imparts drip-free properties to synthetic resin molded articles. The surface of molded synthetic resins such as polyethylene, polypropylene, polyvinyl chloride, polyester, and polymethyl methacrylate is hydrophobic and has little affinity for water, so water droplets tend to adhere to it.
For example, when a synthetic resin film or sheet is used for an agricultural greenhouse or the like, water vapor evaporating from soil or crops condenses on the surface of the film or sheet to form water droplets. As a result, the transmittance of sunlight decreases, hindering the growth of crops, or causing leaf rot due to falling water droplets. Conventionally, in order to prevent water droplets from adhering to such synthetic resin moldings, there have been methods of kneading surfactants and hydrophilic polymer compounds into the synthetic resin before molding, and coating-type non-droplet coating on the surface of the molded synthetic resin. There was a method of applying the agent. Various types of spray-on type non-drop agents have been proposed, including those containing various inorganic colloidal particles and various surfactants.
No. 11348, Japanese Patent Application Publication No. 56177, and Patent Application No. 1983-
174577 etc.). In order to industrially advantageously produce a dropless film or sheet by coating a coated type non-droplet agent containing such inorganic colloidal particles and a surfactant onto a synthetic resin film or sheet, it is necessary to apply the dropless agent to a synthetic resin film or sheet. The method of continuously coating the surface of a film or sheet and drying is the most efficient and excellent method. but,
There is a problem in continuously applying the above-mentioned surface-coating type non-droplet agent containing inorganic colloidal particles and a surfactant to a synthetic resin film or sheet. In other words, when this type of dropless agent is continuously applied to a synthetic resin film or sheet (hereinafter simply referred to as "film") by the roller touch method or dipping method and dried, such a dropless agent is It is not always possible to apply the dropless agent quickly and smoothly, and if the applied non-droplet comes into contact with a guide roll etc. before it is completely dry, the carefully applied non-droplet agent may be absorbed by the guide roll etc. It was found that the dried film did not exhibit a sufficient drop-free effect because almost no droplets were left on the film surface.
In order to completely dry the applied dropless agent before it comes into contact with the guide roll etc., it is necessary to slow down the winding speed or to increase the distance between the coating device and the guide roll. However, the former method results in a decrease in production efficiency, and the latter method has the disadvantage that the equipment becomes larger, and as a result, the factory site and buildings inevitably become larger. Another method is to increase the hydrophilicity of the film to increase the hydrophilicity with the dropless agent, for example, by treating the film surface with corona discharge, or by adding surfactant to the synthetic resin for the film in advance. There are methods such as kneading the agent. However, pretreatment such as corona discharge treatment requires large-scale equipment and is relatively ineffective. Further, the method of kneading a surfactant in advance can improve the applicability of the dropless agent, but another drawback is that the long-term sustainability of the dropless agent is lost. This is presumed to be due to the presence of a water-soluble surfactant between the film and the dropless agent coating. The present inventors have conducted various studies to improve the above-mentioned drawbacks when attempting to continuously apply a dropless agent containing inorganic colloid particles and a surfactant to a synthetic resin film, etc., and have found that a dropless agent containing inorganic colloidal particles and a surfactant is By bringing the inorganic aqueous sol, which has been previously treated to impart deposition properties, into contact with the surface of the film, etc. to which the agent is to be applied, and depositing the particles of the inorganic aqueous sol on the surface of the film, etc., the purpose can be achieved. Knowing what could be achieved, they arrived at the present invention. That is, the present invention provides a method for producing a dropless synthetic resin molded article by applying a dropless agent containing inorganic colloidal particles and a surfactant to a synthetic resin molded article, in which a droplet-free agent is applied to a synthetic resin molded article prior to applying the dropless agent. Synthesis with excellent dropless properties, characterized by bringing an inorganic aqueous sol, which has been previously subjected to a deposition treatment, onto the surface of a synthetic resin molded product to deposit particles of the inorganic aqueous sol on the surface of the synthetic resin molded product. This is a method for manufacturing a resin molded product. According to the method of the present invention, when an inorganic aqueous sol that has been previously treated to impart deposition properties is brought into contact with the surface of a synthetic resin molded article before the application of a dropless agent, the sol is Deposition (precipitation) of sol particles immediately occurs, and the surface of the molded article is covered with the deposited particles. The surface of the molded product covered with such sol particles is easily wetted by water, and the non-droplet agent can not only be applied to the surface extremely easily and smoothly, but also
For example, even if a dripless agent applied thereon comes into contact with a guide roll or the like in a half-dried state, the dripless agent will no longer be absorbed by the guide roll and removed. Therefore, by using the method of the present invention, not only can the application of the dropless agent itself be performed easily and smoothly at high speed, but also the film winding speed can be slowed down, or the distance between the application device and the guide roll can be reduced. There is no need to make the film long, and a significant effect can be obtained in that a dropless film can be continuously manufactured with high efficiency using a compact device. The synthetic resin molded product in the present invention is a molded product of synthetic resin such as polyethylene, polypropylene, polyvinyl chloride, polyester, polymethyl methacrylate, etc. The shape of the molded product includes, for example, a film, sheet, plate, etc. However, it is of course not limited to these exemplified synthetic resins or exemplified shapes. In the present invention, examples of the inorganic aqueous sol that is brought into contact with the surface of the synthetic resin molded product before the application of the dropless agent include silica sol, alumina sol, water-insoluble lithium silicate sol, iron hydroxide sol, and tin hydroxide sol. Particularly preferred aqueous sols are silica sols, alumina sols and water-insoluble silicate sols. Furthermore, in the present invention, the inorganic aqueous sol that has been previously treated to impart deposition properties refers to the inorganic aqueous sol that has been subjected to a treatment to facilitate the deposition (precipitation) of sol particles on the various inorganic aqueous sols as described above. means. As a treatment for facilitating the deposition (precipitation) of such sol particles, there may be mentioned a method of adding various substances to the sol in small amounts, including a substance commonly referred to as a coagulant for the sol. Of course, the substance to be added differs depending on the type of sol, etc. Usually, acids, alkalis, salts, surfactants, and other organic substances such as ethanol and acetone are appropriately selected and used depending on the type of sol. In other words, an inorganic aqueous sol is generally one in which the above-mentioned inorganic substances are dispersed in the form of fine particles in an aqueous medium using various methods, if necessary with the addition of a surfactant, etc. The sol particles remain relatively stable. However, even if the pH is adjusted simply by adding a small amount of acid or alkali, sol particles may become more likely to deposit (precipitate). In addition, the aqueous sol has a positive or negative charge, and aggregation is prevented by the electric repulsion between particles.
Some sols remain stable, and in the case of such sols, adding a small amount of a substance that neutralizes the charge neutralizes the charge of the sol particles, resulting in deposition (precipitation).
It becomes easier to wake up. For example, if a trace amount of an anionic surfactant is added to a positively charged aqueous sol such as alumina sol, or a trace amount of a cationic surfactant is added to a negatively charged aqueous sol such as silica sol, Also, the deposition (precipitation) of sol particles is likely to occur. In the present invention, when the surface of a synthetic resin molded product is brought into contact with such an inorganic aqueous sol that has been subjected to a deposition treatment, sol particles are deposited (precipitated) on the surface of the molded product as described above, and the molded product is The surface is easily covered by sol particles. Various methods can be used for the contact, but two methods that are usually convenient are applying an aqueous sol to the surface of the synthetic resin molding, and immersing the synthetic resin molding in an aqueous sol. can give. For example, in the case of synthetic resin films and sheets, an aqueous sol may be continuously applied to the film or sheet by a roll-touch method, or the film or sheet may be immersed in an aqueous sol and passed through it continuously. You can. Generally, in order to perform a deposition treatment, it is preferable that no surfactant is added to the inorganic aqueous sol, or that the amount of surfactant added is reduced. When there is little surfactant, the surface tension of the liquid is generally 60
It is large, about ~70 dynes/cm, and brushing or spraying is not effective as it is repelled, so it is most preferable to use a method in which a film or sheet is immersed in an aqueous sol and passed through it continuously. Since the inorganic aqueous sol of the present invention has been subjected to a deposition treatment in advance, the sol particles can be easily and uniformly deposited on the surface of the synthetic resin molded article even by extremely short contact, and the sol particles can be coated with the particles. be able to. For example, in the case of the above-mentioned immersion treatment of films and sheets, the purpose can usually be achieved by immersion for about 10 to 60 seconds. In the present invention, a dropless agent is then applied to the surface of the synthetic resin molded article on which sol particles have been deposited by contact treatment with such an aqueous sol. The dropless agent can be applied to the undried wet surface, or the non-droplet agent can be applied after drying the surface on which the sol particles are deposited. In addition, in the case of contact treatment using a highly concentrated inorganic aqueous sol, the molded product after the contact treatment is once rinsed in water for about 5 seconds, and then A dropless agent may be applied as described above. That is, the deposited particle layer obtained by contact treatment using a highly concentrated aqueous sol may be undesirably thick. In general, the thinner the deposited particle layer is, the less rough it is, the less the particle layer peels off due to friction, etc., and the transparency of the film after coating with a dropless agent and drying is better. Therefore, if the deposited particle layer is too thick, it is desirable to perform rinsing treatment with water as described above to remove excess particles. Even with such rinsing treatment, all of the particles are not removed, so the effect of the contact treatment with the aqueous sol is not lost. This is confirmed by the fact that the surface of the molded product after rinsing treatment still retains the property of becoming wet with water. Additionally, when contact treatment is performed using an aqueous sol containing a surfactant, the surfactant may adhere to the particles deposited on the surface of the molded product with the hydrophobic groups facing outward. This may cause the contact treated surface to repel water. Even in such cases, rinsing with water is preferable because the surfactant is removed. Next, the dropless agent used in the present invention mainly contains hydrophilic inorganic colloid particles such as silica, alumina, water-insoluble lithium millicate, iron hydroxide, tin hydroxide, titanium oxide, and barium sulfate, and a surfactant. Examples include those in which these are dispersed in a dispersion medium such as water or alcohol. Preferred dropless agents contain either colloidal silica, colloidal alumina, or colloidal insoluble lithium silicate at a concentration of 0.1 to 20% by weight, preferably 0.5 to 10% by weight, and 0.1 to 20% by weight, preferably is an aqueous sol containing 0.1 to 5% by weight of a surfactant, which is further supplemented with water-soluble lithium silicate and/or a general formula (In the formula, R ¹ is an alkyl group or aryl group having at least one reactive group selected from an amino group, an epoxy group, an epoxy group-containing group, a ureido group, an ammonium group, and an ethylenically unsaturated bond-containing group) as a substituent. R ² and R ³ each represent an alkyl group having 1 to 3 carbon atoms, and R ²
and R ³ may be the same or different. n represents an integer of 1 to 3. ) It is more preferable to add 0.01 to 5% by weight of a silane derivative represented by the following formula. Due to the contact treatment with the inorganic aqueous sol in the present invention, the surface of the synthetic resin molded article is easily wetted by water, so the dropless agent of the present invention can be applied even if no surfactant is blended. is possible.
However, since the non-drop agent containing a surfactant produces less roughness of the coating film of the non-drop agent, a surfactant is added to the non-drop agent used in the present invention. Various surfactants can be used as the surfactant. however,
Addition of cationic or amphoteric surfactants to silica sols or insoluble lithium silicate sols, and addition of anionic or amphoteric surfactants to alumina sols should be avoided. In such a combination, the sol often breaks down and becomes gelled, making it difficult to apply. However, if the sol concentration and surfactant concentration are lowered, the gelation can be kept to a cloudy level, making it possible to apply. Even so, there is a problem with the transparency of the dropless coating after drying. Furthermore, when the silane derivative represented by the above general formula () is added to the non-droplet agent used in the present invention,
It is possible to prevent roughness after drying, and further improve the duration of drip-free properties. Further, when water-soluble lithium silicate is added, its binder effect helps the colloidal particles of the dropless agent to stick, thereby improving the sustainability of the dropless effect. Dropless agents that are particularly suitable for use in the present invention include (1) adding a nonionic or anionic surfactant, a water-soluble lithium silicate, and/or a silane derivative represented by the above general formula () to silica sol; (2) nonionic or cationic surfactant and water-soluble lithium silicate in alumina sol and/or the above general formula ()
and (3) a non-droplet agent in which an anionic or nonionic surfactant is added to a water-insoluble lithium silicate sol. The water-soluble lithium silicate and water-insoluble lithium silicate used as components of the inorganic aqueous sol and dropless agent of the present invention refer to those described below. That is, lithium silicate is obtained by melting silicon dioxide (silica sand, etc.) together with a lithium salt, especially lithium carbonate, and is represented by the general formula Li ₂ O.nSiO ₂ . Depending on the blending ratio of silicon dioxide and lithium salt, different water solubility can be obtained, and in the above formula, n=
Those in the range of 6 to 10 are water insoluble, and n=
Those in the range of 2 to 6 are water-soluble, and the former are used as particle components for the inorganic aqueous sol of the present invention and as inorganic colloid particles of the dropless agent of the present invention, and the latter are used as the inorganic colloid particles of the non-droplet agent of the present invention. It is used as a binder component for dropless agents. Next, an example will be given and explained. % in the examples indicates weight % unless otherwise specified. Example 1 A commercially available silica sol (Nissan Chemical Industries, Ltd., trade name Snotex 40) was diluted with water, and then an aqueous solution of a cationic surfactant (Asahi Glass Co., Ltd., trade name Surflon S-121) and polyoxyethylene (5) lauryl were diluted with water. A treatment for imparting deposition properties was carried out by adding an aqueous solution of ether (special grade reagent). The resulting aqueous silica sol contained 4% colloidal silica, 0.02% cationic surfactant, and 1.2% polyoxyethylene (5) lauryl ether. Agricultural low-density polyethylene inflation film was continuously immersed in this aqueous silica sol for 30 seconds, then rinsed by continuous immersion in water for 5 seconds, and dried with warm air at 60°C. I wound it up. Since the film was wet with water after rinsing, it was confirmed that colloidal silica particles were deposited on the film. In addition, seven types of dropless agents shown in Table 1 below were prepared.

【table】

【table】

[Table] Each of the dropless agents shown in Table 1 was applied continuously by a roller touch method to the above-mentioned low-density polyethylene film on which colloidal silica particles were deposited by contact treatment with silica sol. In addition, for comparison, the same film that had not been subjected to silica sol deposition treatment was also coated in the same manner. The coating conditions were as follows. Film winding speed: 10 m/min Drying method for coated film: Distance between 60°C hot air coating roll and first guide roll: 3 m Under these conditions, the non-droplet coating on the film will be completely removed by the time it reaches the first guide roll. It wasn't completely dry. In the case of films that have not been deposited with silica sol, it is not always easy to apply the dropless agent uniformly, and once the dropless agent has been applied almost uniformly, it remains half-dried on the guide roll. Due to the contact, the drop-free agent was absorbed by the guide roll, and the dried film did not exhibit any drop-free properties. On the other hand, in the case of a film on which colloidal silica particles were deposited, it was extremely easy to uniformly apply each type of non-droplet agent. is not absorbed by the guide rolls, and the dried films made with any of the drip-free agents exhibit excellent drip-free properties. Also, no clouding caused by water vapor occurred. In addition, in the case of a film that has not been treated with silica sol, in order to obtain a film with no-drop properties, it is necessary to contact the guide roll after the applied no-drop agent has completely dried. It was necessary to make the distance between the first guide rolls 6 m or more, or to reduce the winding speed to 12 m/min or less. Example 2 A commercially available alumina sol (trade name Alumina Sol-100, manufactured by Nissan Chemical Industries, Ltd.) was diluted with water, and an anionic surfactant (trade name Surflon S, manufactured by Asahi Glass Co., Ltd.) was added to this.
113) and an aqueous solution of polyoxyethylene (10) nonyl phenyl ether (reagent special grade) were added to give a depositing property. The resulting aqueous alumina sol contained 5% colloidal alumina, 0.02% anionic surfactant, and 1.2% polyoxyethylene(10) nonylphenyl ether. Using this aqueous alumina sol, contact treatment with a polyethylene film was carried out in the same manner as in Example 1, and each of the dropless agents shown in Table 1 was applied in the same manner. The results showed the same drip-free properties as the film of Example 1. Example 3 After diluting a commercially available water-insoluble lithium silicate sol (Nissan Chemical Industries, Ltd. trade name: Lithium Silicate-45) with water, an aqueous solution of an amphoteric surfactant (Asahi Glass Co., Ltd. trade name: Surflon S-131) and polyoxy Depositability treatment was carried out by adding an aqueous solution of ethylene (6) lauryl ether. The resulting aqueous lithium silicate sol contained 5% colloidal silicate and 0.02% amphoteric surfactant and 1.2% polyoxyethylene (6) lauryl ether. Using this aqueous lithium silicate sol, a polyethylene terephthalate film was subjected to contact treatment in the same manner as in Example 1, and each of the dropless agents shown in Table 1 was applied in the same manner. The results showed the same drip-free properties as the film of Example 1. Example 4 Colloidal silica was deposited on agricultural polyvinyl chloride film in the same manner as in Example 1 using an aqueous silica sol subjected to the same deposition treatment as in Example 1, and after rinsing in water for 5 seconds, immediately 1
Each of the dropless agents was applied and dried in the same manner as in Example 1. Each of the obtained films showed the same drip-free properties as in Example 1.

Claims (1)

[Scope of Claims] 1. In a method for producing a dropless synthetic resin molded article by applying a dropless agent containing inorganic colloidal particles and a surfactant to a synthetic resin molded article, prior to applying the dropless agent, An inorganic aqueous sol that has been previously subjected to a deposition treatment is brought into contact with the surface of the synthetic resin molded product to deposit particles of the inorganic aqueous sol on the surface of the synthetic resin molded product. A method for manufacturing synthetic resin molded products. 2. The method according to claim 1, wherein the inorganic aqueous sol treated to impart deposition properties is a silica sol, an alumina sol, or a water-insoluble lithium silicate sol. 3 The dropless agent is a silica sol containing a nonionic or anionic surfactant and a water-soluble lithium silicate and/or a general formula (In the formula, R ¹ is an alkyl group or aryl group having at least one reactive group selected from an amino group, an epoxy group, an epoxy group-containing group, a ureido group, an ammonium group, and an ethylenically unsaturated bond-containing group) as a substituent. R ² and R ³ each represent an alkyl group having 1 to 3 carbon atoms, and R ²
and R ³ may be the same or different. n represents an integer of 1 to 3. ) or a nonionic or cationic surfactant to alumina sol and water-soluble lithium silicate and/or (In the formula, R ¹ is an alkyl group having at least one reactive group selected from an amino group, an epoxy group, an epoxy group-containing group, a ureido group, an ammonium group, and an ethylenically unsaturated bond-containing group as a substituent, or Indicates either aryl group.R ² and R ³
each represents an alkyl group having 1 to 3 carbon atoms,
R ² and R ³ may be the same or different. n represents an integer of 1 to 3. ) The method according to claim 1 or 2, which is a dropless agent to which a silane derivative represented by: .