KR20000026518A - Preparation method of polypropylene sheet for transparent case - Google Patents

Abstract

PURPOSE: A preparation method of a polypropylene sheet for a transparent case is provided which prevents a blocking phenomenon between sheets and gives print ability to sheets by coating-treating one side of a sheet with a fine particles-containing polymeric aqueous solution. CONSTITUTION: A preparation method of a polypropylene sheet for a transparent case comprises (a)melt-extruding a resin composition added from 1 to 10 by weight of an alpha-olefin copolymer to a polyolefin resin having a melt index of from 1 to 20(g/10min) and a melting point of from 140 to 180°C and forming to give a sheet, (b)corona discharge treating the sheet to give a surface tension of 38 dyn/cm, and (c)coating a polymeric aqueous solution containing from 0.1 to 1% by weight of fine particles having a particle diameter of from 0.1 to 0.5 micrometer and from 10 to 50% by weight of an acrylic resin on one side of the sheet. The thus obtained product has a transparency of from 1.5 to 5% haze within a range of from 100 to 500 micrometer in thickness and is excellent in print ability and adhesive property.

Description

Manufacturing method of polypropylene sheet for transparent case

The present invention relates to a method for producing a polypropylene sheet that can be used as a base material for various cases such as cosmetics, toothbrushes, toys, stationery, etc., with excellent printability, adhesion, and transparency.

Gradually, as society became more modern and organized, it became more demanding for convenience and efficiency than a simple, lifestyle-oriented way of life, and as a result, general purpose of packaging, stationery, office supplies, electrical appliances, tools, toys, etc. The market demand for plastic sheets is gradually increasing. In particular, in recent years, the demand for plastic products with excellent transparency, which can see the contents at any time, in order to differentiate from luxury and existing products is rapidly increasing. Plastics that can be used for this purpose include polystyrene, polyvinyl chloride, polypropylene, polycarbonate, polyalkylene terephthalate, and the like. Among these, polyvinyl chloride has the advantages of low cost, easy processing, no special technology or equipment, and excellent post-processability, especially printability and adhesion. Due to the large amount of plasticizers, legal regulations have recently been intensifying, especially in the Japanese market, the demand has sharply decreased due to the tightening of legal regulations. In addition, polystyrene has good transparency and mechanical properties, but has a disadvantage in that it causes odor in the manufacturing process and generates black smoke, ash, dust, etc. during incineration, and causes environmental problems as well as easily broken when stored in a refrigerated condition. In addition, polyalkylene terephthalate is excellent in transparency, but the price is high, the touch is stiff, and it is difficult to determine the working conditions due to the whitening phenomenon generated during processing.Polycarbonate has excellent mechanical properties and transparency, but is also expensive. And since the post-processing is difficult, there are a lot of problems to be solved to be widely used.

Accordingly, olefin resins are the most popular as alternative resins that can satisfy the customer's requirements while solving the above-mentioned problems. In particular, polypropylene resins are not only harmless but also have excellent processability. The range of use and usage is rapidly diversifying and widening. However, the existing polypropylene resin composition and sheet manufacturing method cannot obtain the printability and transparency like the conventional polystyrene or polyvinyl chloride, and in particular, it cannot give the most important adhesive property in the case manufacturing process. There has been a limit to satisfy the needs of consumers.

Based on this theory, the technique disclosed for imparting printability is disclosed in Japanese Patent Laid-Open Publication Nos. 60-24946 and 6-125630 to improve the printability by using a random polypropylene resin to increase surface tension. In 166157, a mixture of syndiotactic polypropylene has been used. However, the use of random polypropylene with high ethylene content gives a certain level of transparency and printability, but under high temperature and high humidity conditions, ethylene groups are transferred to the sheet surface, blocking phenomenon occurs, and heat resistance and post-processability are poor, resulting in poor processability. Diotactic polypropylene is still in its early stages of development and has problems with productivity and economics for industrial application.

In order to improve this problem, the present inventors have diligently researched and added an α-olefin copolymer to a resin containing a propylene composition as a main component and down-regulated the crystallinity of the sheet surface, and then applied one surface of the sheet with an aqueous polymer solution containing fine particles. The present invention has been found to prevent blocking between sheets and impart printability to sheets, thereby completing the present invention.

An object of the present invention is to provide a method for producing a polypropylene sheet for transparent case which is excellent in printability and adhesiveness and has high transparency.

In order to achieve the above object, in the present invention, a resin composition obtained by adding 1 to 10% by weight of an α-olefin copolymer to a polypropylene resin having a melt index of 1 to 20 (g / 10 minutes) and a melting point of 140 to 180 ° C. After melt extrusion and molding, the sheet is corona discharged to have a surface tension of 38 dyn / cm or more, and then 0.1 to 1 wt% of particles having a particle diameter of 0.1 to 0.5 μm on one side of the sheet and an acrylic resin. It provides a method for producing a polypropylene sheet for transparent case substrate, comprising applying a polymer aqueous solution containing 10 to 50% by weight.

Hereinafter, the present invention will be described in more detail.

Polypropylene resin is the lightest and most transparent of the density of 0.90 to 0.92 g / cm3 among general purpose plastics, so it is not only excellent in heat resistance, electrical insulation, chemical resistance and bending resistance, but also harmless and non-toxic and has excellent workability, but it has high impact resistance. There is a weak point. Recently, ethylene and other olefinic monomers have been copolymerized to compensate for these drawbacks.They are classified into homopolymers, random copolymers, and impact copolymers according to the presence and structure of the low molecular copolymers. The high stiffness and good random copolymer have good transparency but low crystallinity, melting point, and stiffness, and impact copolymer has particularly good impact resistance. In the present invention, any kind may be used and mixed use may be used depending on the intended use. However, it is preferable to achieve the object of the present invention to use a propylene copolymer resin having a melt index of 1 to 20 (g / 10 minutes) and a melting point of 140 to 180 ° C. in order to satisfy the properties and required levels of the stretched film. . To the polypropylene resin composition of the present invention, known additives, such as antistatic agents, antioxidants, UV stabilizers, nucleating agents, etc., may be added to the polypropylene resin composition according to the purpose of use and management properties within a range that does not impair the effects of the present invention. Can be.

Incidentally, the α-olefin copolymer used in the present invention is used in an amount of 1 to 10% by weight. If less than 1% by weight can not improve the adhesive properties of the sheet, if more than 10% by weight not only spots (die-line) occurs on the surface of the sheet, there is a problem that the blocking phenomenon between the sheets. The butene, hexene or octene is preferable as the α-olefin monomer for polymerization used in the preparation of the α-olefin copolymer.

In order to manufacture the resin composition in a sheet form by melt extrusion and molding, all existing molding machines may be used, but in particular, it is preferable to use a Δ-type belt type sheet molding machine. High glossiness of the surface of the sheet is the most important to improve transparency.To this end, the surface of the roll or belt contacting the sheet is not only mirrored, but also the sheet and the roll or the belt are in close contact with each other to obtain sufficient transfer and crystal suppression effect on the surface of the sheet. It should be. To this end, it is necessary to set the process conditions for forming the sheet while inducing the pooling phenomenon of the resin.

Accordingly, in the present invention, the polypropylene resin composition is discharged at a speed of 250 to 300 kg per hour under the conditions of an extrusion temperature of 200 to 250 ° C. and a screw rpm of 100 to 150, and the discharged product is transferred to a cooling roll of 15 to 40 ° C. By quenching and attaching to a rotating belt at a speed of 10 to 30 m / min to form a sheet of constant thickness.

The temperature and residence time of the process are the major factors that determine the transparency of the sheet. If the extrusion temperature is too high, the cooling time is delayed, the content of β crystals is lowered, and the transparency is lowered. On the contrary, if the extrusion temperature is too low, the extrusion pressure is increased, resulting in a large load on the equipment. On the other hand, if the temperature of the belt surface is high, the peeling between the roll and the sheet is not smoothed, and a reverse winding phenomenon occurs. On the contrary, if the temperature is too low, the adhesion between the roll and the sheet is poor, resulting in poor surface gloss and transparency. In addition, the present invention has to use a quenching condition to improve the transparency, there is a possibility that the adhesion is poor in the case finishing process of the post-process due to the large amount of propylene of β crystal structure on the sheet surface, but in the present invention The α-olefin copolymer used provides the effect of improving the suitability of polypropylene with such an adhesive. Adhesion between sheets may be performed by ultrasonic treatment or adhesive method, and the adhesive method by ultrasonic treatment has a problem that productivity is low due to too slow production speed. Thus, a method of adding an adhesive to a surface between sheets is mainly used. The main components of the adhesive used for bonding the polypropylene sheet include urethane, acrylic, polyester, and the like, and any of these may be selected and used.

Since the transparency, slip and blocking properties of the resin sheet are generally in a mutual relationship with each other, the two properties cannot be satisfied by simple molding conditions. Accordingly, a sheet having improved transparency by the above-mentioned molding conditions requires a technology of reducing contact area or lowering surface energy in order to improve slip resistance and blocking resistance between sheets. The aqueous solution is coated with the following structure.

The coating method used may be a known coating method such as roll coating, knife coating, extrusion coating, spray coating or curtain coating, but in particular, the roll method is most preferable in terms of processability and workability.

The aqueous polymer solution applied to one side of the sheet according to the present invention specifically includes fine particles and an acrylic resin. Particulates are used to prevent blocking phenomenon between sheets and to maximize the activating effect. Particles having a particle size in the range of 0.1 to 0.5 μm are used in the range of 0.1 to 1 wt%. If it is larger than 0.5 mu m, the transparency of the sheet is lowered. In addition, when the addition amount of the fine particles to be used is less than 0.1% by weight, the blocking improvement effect cannot be obtained, and when it exceeds 1% by weight, the sheet transparency is inferior. As the fine particles, at least one selected from alumina, silica, calcium carbonate, and polymethyl methacrylate having excellent dispersibility may be used.

Acrylic resins used in the aqueous polymer solution for coating according to the present invention are acrylic acid, methacrylic acid, itaconic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hydroxypropyl acrylate , Methyl methacrylate, isobutyl methacrylate, 2-hydroxyethyl methacrylate, polaridyl methacrylate, styrene, vinyl acetate, acrylamide or derivatives thereof, and the like. It is preferable to emulsify-polymerize with having acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, acrylamide and glycidyl methacrylate as main monomers. The acrylic resin preferably has an average molecular weight in the range of 10,000 to 300,000 and a glass transition temperature in the range of 30 to 100 ° C., more preferably in the range of 20,000 to 200,000. If the average molecular weight is less than 10,000, the resin is too hard to increase the hardness of the film surface too high, resulting in poor adhesiveness. The amount of use is preferably 10 to 50% by weight in the coating liquid, and if the amount is less than 10% by weight, there is a problem that the coating layer should be thickened.

In the coating liquid, other additives known in the art, such as antistatic agents, wetting agents, surfactants, pH adjusting agents, antioxidants, dyes, pigments, slip agents, etc. It can mix and use within the range which does not harm.

As for the said application layer, 100-300 Pa is preferable. If it is thinner than 100 mW, printability is inferior, and if it is thicker than 300 mW, drying is required for a long time, which leads to a lot of equipment and productivity, and adversely affects workability of post-process.

In order to improve the coating process, a film tension of 38 dyn / cm or more is required on the film coating surface. In particular, polypropylene resin has a very low surface tension unlike nylon or polyester. Particular preference is given to corona discharge treatment as a pretreatment. Corona discharge treatment affects the coating state depending on the treatment conditions or methods, so careful care and conditions are required.

Polypropylene sheet prepared according to the production method of the present invention has a haze value of 1.5 to 5% in the thickness range of 100 to 500 μm, very transparent, excellent adhesion and printability can be useful as a transparent case substrate have.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples, and various performance evaluations of the sheets prepared in Examples and Comparative Examples of the present invention were performed by the following method.

(1) haze

The haze of the sheet was measured by the following formula using a C-light source by measuring with a haze meter of Gardner Neotek (USA).

Haze = scattered light / (transmission light + scattered light)

(2) friction coefficient

The friction coefficient with the metal friction plate was measured using the surface tester (model name Heidon-14) of the Heidon company (Heidon, Japan) on the load of 205g and the speed of 150 mm / min at the temperature of 135 degreeC.

(3) Blocking resistance

100 sheets (10 cm x 10 cm size) of sheets were superimposed and left standing for 24 hours in a temperature of 25 ° C., a relative humidity of 50% and a pressure of 1 kg / cm ² .

○: good (no occurrence at all)

△: blocking of 10% or less of the total area occurs

×: Blocking of 10% or more of the total area occurs

(4) adhesive

Cut the sheet to the size of 20 cm x 20 cm, melt the urethane-based adhesive at 190 ° C between the inner and outer surfaces of the sheet, apply a thickness of 0.01 mm to the size of 20 cm x 5 mm, and press under a load of 5 kg / mm ² . Next, the obtained sheet was allowed to stand at a temperature of 25 ° C. and a relative humidity of 50% for 10 hours, and then adhesiveness was evaluated by measuring tensile strength using a tensile strength meter of Instron of the United States.

(5) printability

Oily type evaluation lacquer comprising 27 parts by weight of water, 10 parts by weight of n-butanol, 25 parts by weight of methyl cellosolve, 10 parts by weight of methyl ethyl ketone, 25 parts by weight of cellulose acetate butyrate and 3 parts by weight of rhodamine ratio (dye) The sheet samples were coated with wire bar # 18 and sufficiently dried for 1 minute at 90 ° C. in a dryer, and then evaluated by drawing 100 scales on the surface using a cross cutter and then attaching and detaching the adhesive tape. At this time, the larger the number of graduations based on the number of remaining graduations which did not peel out of the 100 graduations, the printing (ink) aptitude was evaluated as being good.

100: no peeling at all (excellent)

0: All peeled off (defect)

Example 1

3% by weight of a polybutene copolymer (XR107L, Mitsui, Japan) was added to a homopolypropylene resin having a melt index of 5.7 (g / 10 min) and a melting point of 162 ° C. Screw rpm 120 at 210 ° C. cylinder extrusion temperature and 270 per hour After discharging at the speed of kg, it was press-cooled between a casting roll (cooling) at 25 ° C. and a Δ belt at 120 ° C., and formed into a sheet on a belt rotating at a speed of 15 m / min, and the surface surface had a surface tension of at least 38 Corona discharge treatment was performed while maintaining the voltage and the speed so as to be dyn / cm or more. On the mirror surface of the sheet, an aqueous coating solution in which 20% by weight of styrene methacrylate and 0.3% by weight of polymethyl methacrylate having a particle diameter of 0.2 μm was added to an aqueous solution composed of 15% by weight of isopropylene alcohol and 85% by weight of water in a reverse roll method. Coating at 200 mm 2 yields a 350 μm thick polypropylene sheet.

The physical properties of the sheets thus produced are measured and shown in Table 1. As can be seen from Table 1, the sheets obtained are not only excellent in transparency but also excellent in printability, adhesion, and blocking resistance, and thus require high transparency. It was enough to be used as a material of.

2 to 5 in the implementation

It was carried out in the same manner as in Example 1 except that the manufacturing conditions were changed as shown in Table 1 below. The physical properties of the sheet thus prepared were good as shown in Table 1 below.

Comparative Examples 1 to 6

It was carried out in the same manner as in Example 1 except that the manufacturing conditions were changed as shown in Table 1 below. Sheet physical properties thus prepared were poor as shown in Table 1 below.

Comparative Example 7

The same process as in Example 1 was carried out, but the corona discharge treatment was not performed. Sheet physical properties thus prepared were poor as shown in Table 1 below.

As can be seen from the above, the polypropylene sheet prepared according to the production method of the present invention is excellent in printability and adhesiveness as well as transparency can be usefully used as a substrate for a transparent case.

Claims (6)

The melt composition was melt-extruded and molded into a polypropylene resin having a melt index of 1 to 20 (g / 10 minutes) and a melting point of 140 to 180 DEG C. After the sheet was subjected to corona discharge treatment to have a surface tension of 38 dyn / cm or more, a polymer aqueous solution containing 0.1 to 1 wt% of particles having a particle diameter of 0.1 to 0.5 μm and 10 to 50 wt% of an acrylic resin was formed on one side of the sheet. The manufacturing method of the polypropylene sheet for transparent cases containing applying. The method of claim 1, a process wherein the α-olefin copolymer is derived from butene, hexene or octene. The method of claim 1, The fine particle is at least one selected from the group consisting of alumina, silica, calcium carbonate and polymethyl methacrylate. The method of claim 1, The polypropylene resin composition was discharged at a speed of 250 to 300 kg per hour under an extrusion temperature of 200 to 250 ° C. and a screw rpm of 100 to 150, and the quenched product was quenched by a cooling roll of 15 to 40 ° C., and then 10 to A manufacturing method characterized by attaching to a belt rotating at a speed of 30 m / min to form a sheet. The method of claim 1, The acrylic resin has an average molecular weight of 10,000 to 300,000 range and the glass transition temperature is 30 to 100 ℃ manufacturing method characterized in that. The method of claim 1, A process for producing a polymer, characterized in that the coating in a thickness of 100 to 300 kPa range.