KR20000020537A - Polymer film having improved anticorrosive characteristic - Google Patents

Abstract

PURPOSE: A polymer film having an improved anticorrosive characteristic is provided to use as a wrapping material of a steel product such as all kinds of vehicle components, semiconductor components and so on since it has excellent surface state, productivity and anticorrosive characteristic. CONSTITUTION: A polymer film includes a first resin layer and a second resin layer at the thickness ratio of 1: 9 or 1: 1. Herein, the first resin layer is consisted of a resin that propylene resin having 1 to 20 of a melting index and 140 to 180 deg.C of a melting point is added up with 5 to 20 wt% of dicyclohexylic ammonium nitrite and 0.1 and 1 wt% of inorganic particle having 0.01 to 1 micrometer of a n average diameter. The second resin layer is consisted of a thermal plastic resin. In addition, the inorganic particle is calcium carbonate, silica, polymethyl methacrylate or a mixture of calcium carbonate, silica and polymethyl methacrylate.

Description

Polymer film with excellent antirust properties

The present invention relates to a polymer film having improved antirust properties, and more particularly, to a polymer film having improved rust resistance by having a resin layer in which an ammonium nitrite-based compound and specific inorganic particles are added to a propylene resin.

Among the plastic films used in various industrial materials and substrates today, polypropylene, polyethylene, polyethylene terephthalate, and the like are the most widely used. Especially for packaging, polypropylene film is inexpensive, and is used for printing, deposition, Various packaging materials such as paper can be applied, as well as colorless and odorless. However, the packaging material that can exhibit the rust-preventing effect in the metal products easily corroded by moisture, such as a machine using a film has not been put to practical use yet. Until now, as a method of obtaining rust preventive effect, a method of applying rust preventive paper or rust preventive oil to the surface has been used, and the practical use of rustproof plastic film packaging material having excellent mechanical strength and strong heat resistance has been required.

Accordingly, the inventors of the present invention have found that the antirust property can be improved by adding ammonium nitrite-based compounds and inorganic fine particles to a resin containing a propylene composition as a main component, thereby completing the present invention.

It is an object of the present invention to provide a polymer film having excellent antirust properties.

In order to achieve the above object, in the present invention, 5 to 20% by weight of dicyclohexyl ammonium nitrite and an average particle diameter of 0.01 to 1 μm in a propylene resin having a melt index of 1 to 20 (g / 10 minutes) and a melting point of 140 to 180 ° C. It provides an at least uniaxially oriented polymer film comprising a first resin layer made of a resin to which inorganic particles of 0.1 to 1% by weight is added and a second resin layer made of a thermoplastic resin in a thickness ratio of 1: 9 to 1: 1.

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

Polypropylene as the base resin of the first resin layer in the film of the present invention is the lightest and transparent with the density of 0.90 to 0.92 g / cm ³ among general-purpose plastics, and has only excellent heat resistance, electrical insulation, chemical resistance and flex resistance. It is also harmless and non-toxic, so its workability is very good, but its cold shock strength is weak. Recently, ethylene and other olefinic monomers are copolymerized to compensate for these drawbacks, and are classified into homopolymers, random copolymers, and impact copolymers depending on the presence and structure of the low molecular copolymers. Homopolymers have high crystallinity and melting point and good stiffness, random copolymers have good transparency but low crystallinity, melting point and stiffness, and impact copolymers have particularly good impact resistance. In the present invention, any type may be used, and may be mixed and used according to the purpose of use. However, in order to satisfy the physical properties and the required level of the stretched film, in the present invention, it is preferable 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.

The rust preventive property is to prevent the formation of hydroxide or oxide mainly compounds on the metal surface, and broadly means to prevent the generation of decay products on the metal surface.

In the present invention, an ammonium nitrite-based compound is used as the polypropylene resin for such a rust-preventing effect, and as such, dicyclohexyl ammonium nitrite of fine powder having white crystallinity is preferable. Dicyclohexyl ammonium nitrite has a purity of 98% or more and is excellent in solubility and dispersibility with water or alcohol, and also excellent in thermal stability, and thus can be used in various ways. The addition amount is preferably 5 to 20% by weight, the use of less than 5% by weight can not achieve the effect of the present invention, when used in excess of 20% by weight, the effect is not only lowered, but also mechanical properties are significantly reduced. . The addition method of the dicyclohexyl ammonium nitrite may be added using a known technique, that is, it may be added during the polymerization of the resin, but the polymerization time is delayed and the color tends to become yellow due to side reactions. After manufacturing high-concentration master chip, it is mixed with existing chip.

In addition, fine inorganic particles having an average particle diameter of 0.01 to 1 µm are added to the polypropylene resin of the present invention, and the amount of addition is preferably 0.1 to 1% by weight. Examples thereof include silica, calcium carbonate, polymethyl methacrylate and mixtures thereof, and the form is preferably spherical. If the average particle diameter is less than 0.01㎛ the blocking activity can not be improved due to the film can not be improved, if the average particle diameter is larger than 1㎛ good activity, but there is a problem that the appearance of the film is poor, such as protrusions or transfer on the film surface. . In addition, if the addition amount is less than 0.1% by weight, the effect of the present invention can not be obtained, if it exceeds 1% by weight there is a problem that the transparency and mechanical properties are significantly lowered.

Although polypropylene resin mixed with such additives may be produced in the form of a mono-layer film, it has various surface properties on the resin layer mixed with additives in order to meet market demands that require increased cost and various surface properties. It is preferable to laminate | stack so that thickness ratio may be 1: 9-1: 1 using another thermoplastic resin. If the thickness of the antirust polypropylene resin layer according to the present invention is less than 1/10 of the total film thickness, the antirust effect is lowered.

Other thermoplastic resins laminated with the rustproof polypropylene resin layer include polypropylene, polyethylene, polyester, polyamide, and the like.

In the film production of the present invention, the step-by-step process operation from heat melting to heat setting will be described in detail.

First, each resin layer kneaded according to the object of the present invention is extruded in a conventional manner to make a coextrusion sheet. In general, an extrusion molding machine is used for the hot melt of the molding material, but the molding material may be molded in a softened state without being hot melted. At this time, any one of a single screw extrusion machine, a biaxial coaxial or a two-way extrusion machine can be used, and it is not necessary to install a vent hole, but in general, the single screw series random type has a constant extrusion amount and does not cause deterioration, thereby stabilizing sheet properties. It is preferable to make it possible. In addition, by passing the molten resin through a filter of preferably 100 mesh to 500 mesh, the effects of kneading and foreign material removal can be simultaneously obtained. However, this condition is not limited and should be selected in consideration of the extrusion amount or pressure, and a filter having a suitable shape such as a flat plate or a cylindrical shape can be selected and used. Here, the extrusion conditions are not particularly limited and may be optionally used according to a given situation, but preferably, a temperature in the range of 250 to 280 ° C. is preferable in order to smooth the flow of the inorganic particles. If it is lower than 250 ° C., unmelted resin is present and its melt viscosity is high, so that its thickness becomes uneven. If it is higher than 280 ° C., decomposition phenomenon becomes remarkable and sulfation occurs, causing deterioration and foaming in the extruder. Examples of dies that can be used include a T-die or a ring.

Next, the sheet obtained by extrusion molding is cooled and solidified. In this case, generally, a metal roll using a refrigerant such as a gas or a liquid may be used to uniform the thickness of the sheet or to improve surface properties. The sheet forming method includes a polishing roll method and an air knife method, and the method of forming the sheet may be determined according to physical properties required for the sheet, that is, uniform thickness or surface properties. The cooling temperature is usually in the range of 20 to 60 ° C, and the cooling rate is determined in the range of 3 to 200 ° C / sec depending on the cooling efficiency. If the temperature is below 20 ℃, the cooling rate is faster than necessary and the rigidity of the sheet is momentarily increased, so that the melt may wave during the high degree of solidification, so that it may not be stable. Happens. It is preferable to shape | mold as little as possible as a condition of cooling solidification as possible.

In the present invention, both of the methods of simultaneously or sequentially stretching the cooling-solidified sheet at least uniaxially are possible. Simultaneous stretching is advantageous in order to maintain mechanical properties and balance, but sequential stretching is more preferable in order to increase the uniformity of the thickness. In particular, when multi-stretching in the longitudinal direction, better mechanical properties can be obtained.

In the case of longitudinal stretching, ie, uniaxial stretching in the direction of the continuous film forming line, heating of the sheet surface is required, and the stretching temperature is not particularly limited, but is preferably 140 to 170 ° C, which is a cold crystallization temperature range of the sheet. If the temperature is less than 140 ° C, the amount of heat is insufficient, so that the stretching is poor, such as a line. If the temperature is higher than 170 ° C, crystallization proceeds excessively, and uniform mechanical properties cannot be obtained. Uniaxial stretching using the speed difference of a roll is the method most commonly used among the longitudinal stretching methods, and is excellent in productivity and widely used. Here, longitudinal stretching is performed by using two nip roll speed differences while heating the film which is fixed and guided between at least two nip rolls and the guide roll in the front process of the nip roll or the roll itself. There is no restriction | limiting in particular in draw ratio, Usually, it carries out in 2 to 8 times of range. If the stretching ratio is less than 2 times, the stretching effect cannot be obtained. If the stretching ratio is greater than 8 times, the stretching ratio is excessively oriented in the longitudinal direction, so that the stretching in the transverse direction is difficult.

The film primary stretched in the longitudinal direction is stretched again in the transverse direction, ie, in the direction of 90 ° in the film continuous direction. The stretching method is not particularly limited and may be other methods as well as conventional methods. Among them, tenter transverse stretching is the most common method, and the transverse stretching is performed by fixing both ends of the film with traveling clips, etc., and gradually increasing the distance between the clips at both ends within a suitable temperature range. This is done. The temperature at this time is preferably in the range of 150 to 180 ° C., which is similar or slightly higher than the temperature at the time of longitudinal drawing. If the stretching temperature is too low, the softening is insufficient and the stretching is difficult. On the contrary, if the stretching temperature is too high, the surface is partially dissolved to obtain a uniform thickness. The ratio of the transverse stretching is not particularly limited, but is generally in the range of 3 to 10 times, and in the case of less than 3 times, the mechanical strength in the transverse direction is not sufficient. In the case of using a polypropylene-based resin, since the area draw ratio of the film to the sheet is 40 to 60 times the most preferable in terms of physical properties, it is preferable to determine the draw ratio in the longitudinal direction and the transverse direction based on this. The stretching speed is usually 1 × 10 to 1 × 10 ⁵ % / min.

In addition, the stretching method to be used is various, such as a method using a gas pressure, a method by rolling, etc. can be appropriately adopted or used in combination.

In order to stabilize the physical and chemical properties of the stretched film obtained by stretching under such conditions, it is preferable to perform heat setting at a constant high temperature. Heat setting is a commonly performed method, but most preferably, it is carried out at a temperature of 180 to 200 ° C. for 0.5 to 120 seconds under the tensioned state, relaxed state, or limited shrinkage state of the stretched film. In addition, the heat setting may be carried out two or more times by changing the conditions within the above range, can be carried out in the atmosphere of argon gas, nitrogen gas or mixed gas using them as well as general air. Without this heat setting step, glass transition is particularly susceptible to deformation near temperature, and may be a limitation in post-processing or use. The heat setting temperature most suitable for the film should be determined by the speed of the film passing through the atmosphere, i.e. the treatment time. The treatment time is determined according to various equipment characteristics and process conditions. However, when the heat treatment time is long, deformation and physical properties are observed, such as an increase in film during molding.

Additives, such as an antioxidant, an antistatic agent, and a slip agent, can be added to the resin composition used by this invention in the range which does not impair the physical properties, such as glossiness and printability of a film surface.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are only for illustrating the present invention, and the present invention is not limited thereto. Various performance evaluations of the films prepared in Examples and Comparative Examples of the present invention were performed by the following methods.

(1) haze

Transparency was measured with a haze meter from Gardner Neotek of the United States and expressed in haze value expressed as a percentage value of scattered light / (transmitted light + scattered light) using a C-light source.

(2) coefficient of friction

The friction coefficient was measured under the conditions of 1.0 kg of load and 150 mm / min of speed using the surface tester (model name: 2227001) by Seisakusho (Japan).

(3) strength

Using Instron's UTM Model-4206, a 50 mm long, 20 mm wide, 12 μm thick film was stretched at a rate of 200 mm / cm at room temperature and 65% relative humidity to create a load-elongation chart for film strength. Evaluated.

(4) antirust

The steel plate of 10cm x 10cm, which had been cleaned on the surface, was completely sealed with a sample film, and then allowed to stand for one week in an atmosphere of temperature of 40 ° C and a relative humidity of 70RH%. Evaluated.

◎: No occurrence at all

○: occurs within 5% of total area

Δ: 5 to 10% of the total area

×: more than 10% of the total area

(5) film surface condition

It evaluated according to the ratio of the spot (cloudy phenomenon) which appears in the film 10 cm x 10 cm area.

◎: No occurrence at all

○: Available within 5%

(Triangle | delta): A change of use is possible to 5 to 10%

×: not available in more than 10%

(6) productivity

Productivity was evaluated by the number of breaks during film production with the same composition.

5 times / day or less: ○

5 times / day or more: ×

Example 1

Spherical silica with 8 wt% of fine powder dicyclohexyl ammonium nitrite (product name: TVI, Japan Eastern Chemical) in a homopolypropylene resin having a melt index of 4 (g / 10 min) and a melting point of 155 ° C. The resin composition to which 0.5 weight% was added was made into the 1st resin layer. At this time, the two particles were mixed and kneaded by processing a high-concentration master chip each made alone. A resin composition composed of the same homopolypropylene resin as described above was used as a second resin layer, and the first and second resin layer compositions were discharged at a rate of 270 kg per hour under extrusion conditions of 270 ° C. and 120 rpm, followed by casting at 30 ° C. It was quenched in a roll (cooling) to make a two-layer coextrusion sheet. At this time, an air knife method was used as a molding facility. The quenched sheet was uniaxially stretched 4.7 times in the longitudinal direction at 150 ° C, stretched 8.1 times in the transverse direction at 165 ° C, and then heat-set at 200 ° C so that the thickness of the first resin layer was 1/9 of the total thickness of the film. A polymer film having a total thickness of 20 μm, which is a ratio of 2, was prepared.

The prepared film was evaluated for performance, and the results are shown in Table 1 below.

Examples 2-5 and Comparative Examples 1-5

The polymer film of the same thickness was produced by the same method as Example 1, changing manufacturing conditions as shown in Table 1 below. The performance evaluation results of the films are shown in Table 1 below.

The polymer film according to the present invention, as can be seen in Table 1, not only the surface state and productivity of the film is excellent, but also particularly good rust resistance can be used as a packaging material for steel products, such as various automotive parts, semiconductor parts.

Claims (3)

5 to 20% by weight of dicyclohexyl ammonium nitrite and 0.1 to 1% by weight of inorganic particles having an average particle diameter of 0.01 to 1 μm were added to the propylene resin having a melt index of 1 to 20 (g / 10 minutes) and a melting point of 140 to 180 ° C. At least uniaxially oriented polymer film comprising a first resin layer made of an added resin and a second resin layer made of a thermoplastic resin in a thickness ratio of 1: 9 to 1: 1. The method of claim 1, A film, characterized in that the inorganic particles are silica, calcium carbonate, polymethylmethacrylate or mixtures thereof. A method for improving rust resistance by packaging an iron-containing product using the polymer film according to claim 1.