JPS6028306B2 - resin composition - Google Patents

Description

[Detailed description of the invention]

[1] Purpose of the Invention The present invention relates to a polypropylene resin composition for stretched films. More specifically, the present invention relates to a polypropylene resin composition for stretched films with excellent antistatic properties.

[0] Background of the Invention Compared to unstretched polypropylene films, it is very difficult to provide an effective antistatic effect to stretched products, especially biaxially stretched films. Such special characteristics in preventing static electricity from drawn polypropylene products are such that, for example, when an unstretched product is kneaded with an antistatic agent and molded, a sufficient amount of antistatic agent is required to exert an antistatic effect on the surface of the polypropylene. are almost evenly distributed. Further, the subsequent movement of the antistatic agent present inside the polypropylene to the surface of the polypropylene is often relatively smooth. On the other hand, in a stretched product, the antistatic agent on the surface of the polypropylene is destroyed by the mechanical force during stretching, or its distribution becomes very sparse. Furthermore, due to the molecular orientation of polypropylene, the movement speed of the antistatic agent is extremely slow, so even though it may be sufficiently effective for unstretched products, it has little effect on stretched products. It is presumed that it will not be effective. Based on the above, antistatic effects are imparted by blending a considerable amount of an antistatic agent with a relatively fast migration speed, molding the mixture (composition), and performing strong corona treatment. The method was conventional. Because it contains a high concentration of antistatic agent, it not only generates smoke during molding, but also causes the antistatic agent to bulge out on the surface of the stretched material (bleat), which causes many problems in terms of blocking, food hygiene, etc. cause undesirable phenomena. Therefore, the actual situation is that the applications of the stretched product are limited. Conventional antistatic agents are substances that cannot exhibit their full effect unless they are added in such a large amount that they impair the properties of polypropylene, or they can be sufficiently effective when added in small amounts. Even if the film is capable of achieving this, it may become unusable due to smoke generation during stretch-forming or severe contamination of the equipment due to migration during stretch-forming. (having low bending rigidity) and causing blocking, we found a material that was industrially valuable, but we were unable to produce it. Moreover, if the antistatic effect is improved by using a substance with poor compatibility (for example, paraffin wax) instead of the crystalline wax used in the present invention, the substance may be used in the stretched product. Since it bleeds onto the surface, it not only causes trouble during molding, but also loses the antistatic agent from the surface in the stretching oven, making it less effective. On the other hand, when highly compatible substances such as polyethylene and polyethylene wax are used, the antistatic agent is less effective because it is difficult for the antistatic agent to move near the surface of the stretched material. [m] Structure of the Invention In view of the above, the present inventors have conducted various searches to obtain an excellent polypropylene resin composition for use in stretched films, and as a result, the present inventors have found that wind isotactic polypropylene 1
Part by weight of 0 {B} "Crystalline wax composed of a saturated linear hydrocarbon with a carbon number of 45 to 6 synthesized by the Fischer-Trops method" (hereinafter "crystalline wax")
) 0.5 to 5. parts by weight and [q antistatic agent 0.1 to 2. It has been discovered that a composition consisting of parts by weight of . [W] Effects of the invention In the present invention, the following effects can be achieved when producing a resin composition (generally by melt-kneading), when stretch-molding the composition, and when using a molded product. (Characteristics) to shine. tl' Even if a composition containing as little antistatic agent as possible is stretch-molded, the stretched product not only exhibits a practically effective antistatic effect, but also Does not impair the excellent properties inherent to polypropylene. [2] Even if an antistatic agent that is safe for food hygiene is used, the same effect as above will be achieved. '3 - Only the crystalline wax used in the present invention exhibits an extremely good antistatic effect, and problems such as problems during molding due to smoke generation, blocking of molded products (stretched products), and deterioration of pigs. There are almost no drawbacks. The reason why the composition obtained in the present invention and its stretched product exhibit the above effects is considered to be as follows. [11] This is thought to be because the crystalline wax used in the present invention has a different crystal structure and molecular structure than other waxes and saturated hydrocarbons produced by other methods.
Borip. It has moderate compatibility with pyrene. ■ The mechanism of this action is that the antistatic agent is transferred from the polypropylene that crystallizes first to the crystalline wax when the original fabric is formed, and when it is further stretched, due to the appropriate compatibility, a high concentration of antistatic agent is transferred to the crystalline wax. The wax containing the antistatic agent migrates onto the surface of the drawn object, forming a wax layer containing a relatively high concentration of antistatic agent near the surface. [V] Detailed Description of the Invention Isotactic Polypropylene The isotactic polypropylene used in the present invention is essentially crystalline, and from the viewpoint of bending rigidity, the hebutane extraction residue must be at least 95%. It is desirable, especially 97% or more. Although the polypropylene can be obtained by polymerizing only propylene in the presence of a Ziegler catalyst, it can also be obtained by polymerizing propylene and a small amount of ethylene or other Q-
It can also be obtained by copolymerizing with an olefin (generally having at most 12 carbon atoms). The content of ethylene or other Q-olefin in the copolymer is generally less than 1.0% by weight. Generally, produced homopolymers and copolymers contain a small amount of amorphous (atactic) polymer, and this amorphous polymer is extracted and removed before use. In addition, the polypropylene melt flow index (A
In accordance with STM D-1238-65T, hereinafter “MFI
'') is generally 0.1 to 5.0 evenings/10 minutes, particularly preferably 0.3 to 4.0 evenings/10 minutes.
'B} Crystalline wax The crystalline wax used in the present invention is synthesized by the Fischer-Trops method, and is mainly composed of saturated straight-chain hydrocarbons having 45 to 6 carbon atoms. It is something. The wax is commonly referred to as Fischer Trops wax and is FDA approved. In addition, even if the proportion of hebutane extraction residue in the entire resin composition of the present invention including the crystalline wax used in the present invention is comparable to that of ordinary isotactic polypropylene, the stiffness of the film ( It has also been found that the Young's modulus) is improved. If a wax other than crystalline wax, such as polyethylene wax, is added to highly crystalline isotactic polypropylene and molded, the transparency, which is one of the characteristics of double-stretched polypropylene film, will decrease, and the film will become more Significant decrease in lower back strength. Furthermore, even when other waxes that do not reduce transparency are used, the stiffness of the film inevitably decreases, as with polyethylene wax. That is, if the wax to be added does not have a certain degree of hardness itself, when added to highly crystalline isotactic polypropylene, the stiffness of the formed biaxially stretched film will be lowered. On this point, when a crystalline wax exhibiting a certain degree of hardness is added, the decrease in stiffness of the molding wax can be minimized. Further, when polypropylene wax is used, since the softening point of the polypropylene wax exceeds 14030 (ring and ball measurement method), the effect of improving stretchability is not exhibited during oven stretching at about 160oC. Furthermore, low-molecular-weight substances called plasticizers other than those mentioned above and petroleum resin-based substances emit severe smoke, which hinders their use. 'C' Antistatic Agent The antistatic agent used in the present invention is one that is generally used as an antistatic agent for polyolefins (especially polypropylene films). In particular, when alkylamine compounds, imidazoline compounds, amide compounds, betaine compounds, polyhydric alcohol compounds, and polyester compounds are used in combination with the crystalline wax, a significant improvement in antistatic effect has been observed. This is desirable because it can be used. Among these antistatic agents, those in which the alkyl group has 12 to 1 carbon atoms are preferred.
Typical examples of these antistatic agents include N・N-bis(
8-hydroxyethyl) stearylamine, N・N-bis(8-hydroxyethyl) stearylamide, N・N
-bis(8-hydroxyethyl)stearylbetaine,
Examples include glycerin tristearate, a compound having the general formula shown below, and N.N.N'.N'-tetrakis(8-lauryloxyethyl)m-xylylenediamine. Dish Blending ratio The mixing ratio of the crystalline wax and the antistatic agent to the weight part of the isotactic polypropylene 10 used in the present invention is as follows. Crystalline wax is 0.5-5. parts by weight, especially 1
．． 0-3. parts by weight are preferred. If the blending ratio of crystalline wax is 0.5 parts by weight or less with respect to 10 parts by weight of polypropylene, stretchability cannot be improved and moldability is poor. Also, 5. If the amount is more than 2 parts by weight, the stiffness of the drawn product decreases.
Moreover, the antistatic agent is 0.1 to 2. parts by weight, especially 0.2 to 1. Parts by weight are desirable. 2 for 100 parts by weight of polypropylene. Even if more than 2 parts by weight of antistatic agent is blended, problems such as smoking and staining of the rolls will occur, and the antistatic effect will not be further improved. Furthermore, with conventional compositions, it has been considered almost impossible to have an industrially effective antistatic effect at a concentration within FDA standards, but with the present invention, which uses the crystalline wax in combination, the antistatic effect is industrially effective. It is possible to exhibit a strong antistatic effect. Legs Manufacture, use, etc. of the composition The composition of the present invention can be manufactured by uniformly mixing polypropylene, crystalline wax, and antistatic agent. The mixing method includes dry blending using mixers such as Henschel mixers and tumblers, which are generally used in the field of synthetic resins (especially polyolefins); A method of melt-kneading using a mixer such as a blender is convenient. Furthermore, the effect can be further improved by applying two or more of these mixing methods (for example, a method of pre-mixing with a Henschel mixer and then mixing the resulting mixture using an extruder). Although the composition obtained according to the present invention is obtained by mixing only polypropylene, a crystalline wax, and an antistatic agent, it also contains stabilizers against light (ultraviolet light), heat, ozone, and oxygen, which are generally added to polypropylene. It's okay. Additionally, additives such as solvents and antiblocking agents used in polypropylene may be added depending on the intended use, and such combinations (compositions) are also included in the present invention. Methods for obtaining a stretched product using the composition obtained by the present invention include a method in which an unstretched film is formed in advance and then stretched in one stroke, and a sequential two-mari method in which the first koji stretched product is further stretched in the transverse direction. Examples include a method of stretching, a method of simultaneous biaxial stretching, a method of multilayer stretching in which the single stretched product is laminated and then laterally stretched, and a method of biaxially stretching a multilayer sheet obtained by coextrusion. Further, by subjecting the stretched product obtained by the above method to an appropriate corona discharge treatment, an even better antistatic effect can be obtained. All of these methods are generally known and used methods. As mentioned above, the stretched product obtained by the above method not only has an excellent antistatic effect but also has good bending rigidity, so it can be used as a stretched tape, a single stretched film,
Can be applied to double-stretched films, polypropylene fibers, etc. Furthermore, by using an antistatic agent that is safe for food hygiene, it can be safely used as a food packaging material that comes into direct contact with food, which is of great industrial importance.
[W] Examples and Comparative Examples The present invention will be explained in more detail with reference to Examples below. In the Examples and Comparative Examples, the charge decay rate is the number of seconds it takes for the charge voltage to be halved after being charged for 6 seconds using a Startake Honest meter even when the applied voltage is 10 kilovolts. However, anything that exceeds 9 sands is considered meritorious. Samples aged after 1 or 3 days at a temperature of 40°C were evaluated. In addition, the surface resistivity was measured using a vibrating capacitance type insulation resistance measuring device at a temperature of 20 oo and a relative humidity of 65.
Measured under the condition of %. Samples aged after 1 or 3 days at a temperature of 4000 °C were evaluated. Furthermore, Young's modulus was determined by measuring the tensile modulus using Tensilon. Note that the pulling speed was 10 kites/min. Further, haze was measured according to ASTMK-6714.
The smoke generation property was evaluated as follows by observing the smoke generation state with the naked eye during molding using a T-die. ◎: Excellent ○: Good △: Smoke generation ×: Severe smoke generation In addition, the blocking property was 100 at a temperature of 40 qo.
The degree of blocking after aging for 4 hours under a load of evening/ground was evaluated according to the feeling in the following four grades. ◎: Excellent ○: Good △: Bad ×: Problematic In addition, the stretchability was evaluated by visually observing each molding process and molded film in each Example and Comparative Example using the following four grades. ◎: Good stretchability, no thickness unevenness ○: Good stretchability, a little uneven thickness △: Poor stretchability, a lot of thickness unevenness 2. Comparative Examples 1-1 to 1-12 Polypropylene with an MFI of 2.0 min/1 G [day. R. 96%, hereinafter referred to as "PP'1}"
, polypropylene with MFI of 0.5 evening/10 minutes [Sun. R
．． 96%, hereinafter referred to as “PP■”] or MFI of 2.
0 evening/10 minutes polypropylene [Sun. R. Nada%, hereinafter referred to as “
A saturated linear hydrocarbon [carbon 52 pieces, hereinafter referred to as "substance {a"], paraffin wax [carbon number 3M, hereinafter referred to as "substance [b}"], crystalline wax [solid with carbon number 5, hereinafter referred to as "substance 'c-"] ], low molecular weight polypropylene wax [47 carbon atoms (hereinafter referred to as "substance'd}"), alicyclic saturated hydrocarbon [
Carbon number 60, hereinafter referred to as "substance [e}"], hydrogenated petroleum resin [carbon number Ion solid, hereinafter referred to as "material"]
, terbene resin [solid with 7 carbon atoms, hereinafter referred to as "substance (g)"]
], polyethylene wax [150 carbons,
(hereinafter referred to as "substance (h)")], polypropylene wax (carbon number: 15, hereinafter referred to as "substance (i)"), or low-density polyethylene (density: 0.915 m/g, carbon number: 2100 solid, hereinafter referred to as "substance (i)") "Substance (i)"] (the usage amount of each is shown in Table 1-1), as an antistatic agent "
1:2 mixture of N.N-bis(8-hydroxyethyl)stearylamine and glyceryl monostearate"
(hereinafter referred to as “antistatic agent W”) or N・N-bis (8
-hydroxyethyl) stearyl betaine [hereinafter referred to as "antistatic agent {B}"] 0.6 parts by weight each, and 0.2 parts by weight of 2,6-di-tert-butyl-P-cresol as a stabilizer. 1 part and 0.2 parts by weight of calcium stearate as a processability improver were dry-blended in advance using a Henschel mixer. Each of the obtained mixtures was heated to 22,000 yen using an extruder.
A pellet was made while kneading at a temperature of . Each of the resulting pellets was extruded at a T-die temperature of 250 qo, and a chill roll temperature of 30 qo was used to form an original fabric having a thickness of 150 microns. Each raw fabric was stretched at a temperature of 140 oo over a substantially 5-fold short section between two sets of nip rolls having different circumferential speeds to produce a stretched product (film) with a thickness of 30 microns. Each of the obtained films was corona treated to a surface wetting tension of 39 dynes. The antistatic effect (electrostatic decay rate and surface resistivity after 1 day and 3 days), Young's modulus, haze and blocking properties, smoke generation properties during molding, and stretchability of each film were evaluated first.
- Shown in Table 2. Table 1-1 Table 1-2 Examples 2-1 to 2-7, Comparative Examples 2-1 to 2-13 Parts by weight of the above polypropylene 10, low molecular weight substances and antistatic agents (types and combinations thereof) (The amount is shown in Table 2-1)
In addition, a stabilizer and a processability improver (the same amounts) were mixed in a Henschel mixer under the same conditions as in Examples 1-1. Each of the obtained mixtures was similarly used to create pellets using an extruder. Each of the obtained pellets was heated to a T-die temperature of 2.
Extruded at 5000, chill roll temperature is 0℃, thickness is 12
A 0.00 micron original fabric was molded. Each raw material is heated to 140°C between two sets of nip rolls with different peripheral speeds.
Substantially 5 times short stretch stretching was carried out at a temperature of . Next, after transverse stretching was performed 8 times at a tenter temperature of 160 qC, corona treatment was performed so that the surface wetting tension was 39 dynes, to form a Nito stretched film (thickness: 30 microns). Antistatic effect of each film (after 1 day and after 3
charge decay rate and surface resistivity), Young's modulus,
Haze and blocking properties, smoke generation properties during molding, and stretchability are shown in Table 2-2. Table 2-1 1) Addition of 1.2 parts by weight 2) 0.3 '' 3) 1.0 '' From the Examples and Comparative Examples in Table 2-1 and above, the resin composition obtained by the present invention The stretched film not only can greatly improve the antistatic effect, but also has a J.R. 97
% or more isotactic polypropylene is used as a base, it has good stretchability, and there are no problems with formability. Furthermore, it is stronger than ordinary stretched polypropylene and has good antistatic properties. It is clear that the film is obtained.

Claims (1)

[Claims] 1 (A) 100 parts by weight of isocatic polypropylene (B) Crystalline wax composed of a saturated linear hydrocarbon having 45 to 60 carbon atoms synthesized by the Fisher Tropes method 0.5 to 5 A polypropylene resin composition for a stretched film, comprising 0.0 parts by weight and 0.1 to 2.0 parts by weight of (C) an antistatic agent.