JPH1087903A - Polyolefin resin composition having suppressed heat-discoloring property, production of polyolefin molded material composed of the resin composition and polyolefin vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject composition suppressed in yellowing by heat and capable of reusing a scrap of the molded product by compounding a polyolefin resin containing a nitrogen-containing antistatic agent with a small amount of hydrotalcites. SOLUTION: This composition contains (A) a polyolefin resin, (B) a nitrogen- containing antistatic agent (preferably a hindered amine-based antistatic agent) and (C) hydrotalcites of the formula: Mx Aly (OH)2x+3y-2z (A)z .aH2 O M is Mg, Ca or Zn; A is CO3 or HPO4 ; (x), (y) and (z) are each a positive number; (a) is 0 or a positive number}. Preferably, the composition further contains (D) a metal salt of a higher fatty acid. The mixing amount of each component is 0.01-0.20 pt.wt. of the component B, 0.005-0.15 pt.wt. of the component C, and 0.01-0.30 pt.wt. of the component D, when combinedly using, to 100 pts.wt. of the component A. By using the composition, yellowing of the resin by heat in melt molding can effectively be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin composition in which the heat discoloration is suppressed, and more particularly to a heat treatment during melt molding obtained by adding a nitrogen-containing antistatic agent and hydrotalcites to a polyolefin. The present invention relates to a polyolefin resin composition in which discoloration is suppressed and a polyolefin molded article produced from the polyolefin resin composition as a raw material, particularly a container.

[0002]

2. Description of the Related Art Polyolefin resins are widely used for the production of various molded products such as films, sheets, containers and the like. When producing such molded products, an antioxidant is contained in the polyolefin resin. In addition, ultraviolet absorbers, antistatic agents, heat-resistant agents, fillers, pigments, and other additives are blended. Plastics such as polyolefins are inherently good insulators and are easily charged,
When charged, dust not only adheres and becomes easily contaminated, but also causes a discharge phenomenon, which may cause a large accident such as an explosion in a coal mine. For this reason, it has been proposed that a non-ionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant or the like be blended with the polyolefin as an antistatic agent. However, when a polyolefin resin containing a nitrogen-containing antistatic agent is melt-molded among these antistatic agents, there is a problem that the resin is significantly yellowed. This yellowing is particularly noticeable in polyolefins produced by a so-called deashless process, in which the catalyst removal step is omitted by the use of a highly active catalyst.

Hitherto, it has been known to use a phenolic or phosphite-based antioxidant in combination to prevent a polyolefin resin containing no nitrogen-containing antistatic agent from being thermally degraded, for example, Japanese Patent Publication No. 56-5417. The publication describes a combination of trisaryl phosphite and a phenolic antioxidant. Further, in order to solve yellowing during long-term storage of a polyolefin resin containing no nitrogen-containing antistatic agent, a method of using a specific organic phosphite compound together with an alkyl-substituted phenol-based stabilizer has been proposed. The addition of these conventional antioxidants could not suppress yellowing due to heating during melt molding of a polyolefin resin containing a nitrogen-containing antistatic agent.

[0004]

When manufacturing various molded products from a polyolefin resin, regrind such as burrs, chips, and punched chips at the time of molding is inevitably generated.
These are usually reused in the production of moldings. Also,
In recent years, from the viewpoint of resource saving, polyolefin molded products such as used containers have been collected and reused for manufacturing various molded products. However, if the polyolefin resin yellows during melt molding, these scraps cannot be reused, and depending on the type of molded product such as a non-colored film or sheet, the commercial value of the molded product is marked. May be reduced. For this reason, in order to reuse the resin in which the yellowing has occurred, a special toning process may be required, which results in an increase in cost. Accordingly, an object of the present invention is to suppress yellowing due to heating of a polyolefin resin containing a nitrogen-containing antistatic agent that is liable to cause yellowing during melt molding, and to prevent a decrease in the commercial value of the molded product itself, Polyolefin resin composition that can also reuse scrap,
Another object of the present invention is to provide a molded article such as a container manufactured from the resin composition.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies in view of the above circumstances, and as a result, a polyolefin resin containing a nitrogen-containing antistatic agent is represented by the following general formula (1). The present inventors have found that a polyolefin resin composition satisfying the above objects can be obtained by blending hydrotalcites, and the present invention has been completed. M _x Al _y (OH) _{2x + 3y-2z} (A) _z · aH ₂ O (1) (M is Mg, Ca or Zn, A is CO ₃ or HPO ₄ ,
x, y, z are positive numbers, a is O or a positive number) That is, the present invention provides (A) a polyolefin resin,
(B) a nitrogen-containing antistatic agent and (C) the general formula (1)
Characterized by containing a hydrotalcite represented by the formula, a polyolefin resin composition having suppressed heat discoloration during melt molding, and polyolefin molding such as a container manufactured from the polyolefin resin composition as a raw material It provides things.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin (A) used in the present invention includes homopolymers such as medium / low density polyethylene, high density polyethylene, polypropylene and poly 1-butene, as well as ethylene, propylene, 1-butene and 1-butene. -Hexene, 4-methyl-1-pentene and other α-olefin alternating copolymers, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers and the like. In particular, a remarkable effect is exhibited when each of the above polymers which are polymerized with a highly active Ziegler-based catalyst and have not been subjected to a catalyst removal step, that is, a so-called deashing step, is used. As these polyolefin resins, molding waste such as burrs generated during molding and defective products, and so-called scraps such as re-collected used containers can also be used. These scraps can be used alone in the present invention,
Usually blended with the unused polyolefin resin,
Used as part of the resin component. When these scraps are used, molding at a high temperature and repeated molding as a recovery system cause a problem of discoloration and hue change particularly when a nitrogen-containing surfactant is used as an antistatic agent.

The (B) nitrogen-containing antistatic agent used in the present invention includes a nonionic surfactant, a cationic surfactant, an anionic surfactant and an amphoteric surfactant. Surfactants, amine salts, imidazolines, amine oxide adducts, quaternary ammonium salts, amides, alkylamines and ethylene oxide
Condensates with “EO” may be used. Specific examples thereof include triisopropanolamine, N-cyclohexylamine, cyclohexylamine, tributylamine, monoethanolamine, butylamine, and salts thereof with butyric acid, boric acid, phosphoric acid, ricinoleic acid, and berargonic acid; Hydroxyethyl-2-alkylimidazoline and its adipate, 2-alkylimidazoline and its EO adduct phosphate; ethylenediamine, alkylenediamine,
EO adducts of higher polyamines such as ethylene oxide, propylene oxide (PO) adducts and alkanolamines of lower polyamines such as isopropanolamine and triisopropanolamine; didodecyldipropylammonium bromide, octylcyclohexyldimethylammonium chloride, alkylamine EO Quaternary ammonium salts from adducts; higher fatty acid amides, their EO adducts, dialkylamides, methyliminobispropionamides, benzoic acid-N-methylstearylamides, maloic acid-N-methylstearylethyl esters, alanine-N -Dodecylamide; N-acyl sarcosine (consisting of an acyl group derived from the bound fatty acid of lauryl, oleoyl, coconut oil) N-N-bis (2-hydroxyethyl) alkyl (C12~C18) amine,
N, N-bis (2-hydroxyethyl) alkyl (C14-C18 derived from tallow) amine, N, N-bis (2-hydroxyethyl) dodecaneamide, N, N-bis (2-hydroxyethyl) octadecyl Amine, N-
(2-hydroxyethyl) -N-octadecyl-glycine (monosodium salt), N, N-bis (2-hydroxyethyl) -N- (carboxymethyl) octadecaneamino (internal salt), N-methacryloylethyl-N , N-
Dimethyl ammonium-α-N-methyl carboxylate, octadecyl methacrylate, cyclohexyl methacrylate, N-vinyl-2-pyrrolidone copolymer;
Alanine-type metal salts, imidazoline-type metal salts, diamine-type metal salts, metal salts of alkylamines having an ethylene oxide group, and the like. Among these nitrogen-containing antistatic agents, hindered amine antistatic agents are preferably used, and among them, alkylethanolamines are particularly preferable.

(C) The above general formula (1) used in the present invention
As the hydrotalcites represented by, any of natural products and synthetic products can be used. Specifically,
For example, Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H _{2
O, Mg 5 Al 2 (OH} ) 14 CO 3 · 4H 2 O, Mg 6
Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O, Mg ₈ Al ₂ (O
_{H) 20 CO 3 · 5H 2} O, Mg 10 Al 2 (OH) 22 (C
_{O 3) 2 · 4H 2 O} , Mg 6 Al 2 (OH) 16 HPO 4
・ 4H ₂ O, Ca ₆ Al ₂ (OH) ₁₆ CO ₃・ 4H
₂ O, Zn ₆ Al ₆ (OH) ₁₆ CO ₃ .4H ₂ O, and the like. Alternatively, it may not be represented by the above exact formula, for example, Mg ₂ Al (OH) ₉
· 3H ₂ part of the OH of O may be one was Tsu replace with CO _3. Furthermore, those obtained by removing some or all of the water of crystallization of these compounds may be used. Among them, M is M
g, and it is preferable to use a compound in which A is CO ₃ .

The polyolefin resin composition of the present invention includes:
Further, by blending (D) a higher fatty acid metal salt, discoloration by heating during melt molding can be further suppressed and moldability and the like can be improved. As such a higher fatty acid metal salt (D), an alkali metal salt, an alkaline earth metal salt, a zinc metal salt or the like of a higher fatty acid having 10 to 22 carbon atoms can be used. Specific examples of higher fatty acid metal salts include lauric acid, tridecylic acid, myristic acid, pentadecylic acid,
Palmitic acid, heptadecylic acid, stearic acid, sodium salts such as nonadecanoic acid, potassium salts, magnesium salts, calcium salts, barium salts, zinc salts and the like, among which metal salts of stearic acid, especially using calcium stearate Is preferred.

The mixing ratio of each component in the polyolefin resin composition of the present invention is as follows:
(B) 0.01 parts by weight of nitrogen-containing antistatic agent
To 0.20 part by weight, preferably 0.02 to 0.15 part by weight and (C) hydrotalcites 0.005 to 0.5 part by weight.
15 parts by weight, preferably 0.01 to 0.05 parts by weight, and 0.1% when (D) higher fatty acid metal salt is used in combination.
01 to 0.30 parts by weight, preferably 0.03 to 0.20
Mix by weight. The feature of the present invention is that, among these additives, by blending an extremely small amount of (C) hydrotalcites, a polyolefin resin composition containing a nitrogen-containing antistatic agent, which is unique to a polyolefin resin composition at the time of melt molding. It succeeded in suppressing heat discoloration for the first time. If the amount of the hydrotalcites is less than the lower limit, heat discoloration during melt molding cannot be prevented. On the other hand, when the amount is more than the upper limit, the effect of suppressing heat discoloration is rather reduced, the effect of the antistatic effect is exerted, and the surface of the molded product is roughened. In particular, when 0.01 to 0.05 part by weight of hydrotalcite is blended with respect to 100 parts by weight of the polyolefin resin, an extremely remarkable effect of suppressing heat discoloration can be obtained. INDUSTRIAL APPLICABILITY The present invention is extremely useful for preventing a light-colored container mainly composed of a white pigment from changing its hue. Further, the present invention is useful for preventing a slight change in hue and uneven color even in a dark-colored container.

In the present invention, there is no particular limitation on the method of blending (A) an additive such as hydrotalcites with the polyolefin resin, and a usual method is used. For example,
Hydrotalcites or the like may be added to the base polyolefin resin from the beginning, or a method of preparing a masterbatch together with a coloring agent or the like in advance and blending the masterbatch with the base polymer may be adopted. The composition of the present invention may contain other additives commonly used in polyolefin resins, for example, colorants, fillers, antioxidants, ultraviolet absorbers, flame retardants, plasticizers, and the like.

As means for compounding the components to obtain the composition of the present invention, a ribbon blender, a high-speed mixer, a co-kneader, a pelletizer, a mixing roll, an extruder, an intensive mixer and the like can be mentioned. There is no particular limitation on the method of compounding each component, such as a method of adding to the base polyolefin resin, a method of adding to the colorant masterbatch, a method of preparing and adding an additive masterbatch to the recovered resin, and the like. No. The resin composition of the present invention uses a well-known melt molding machine, a film, a sheet,
It can be formed into any molded product such as a bottle, a tray, and a pipe. As the melt molding method, any molding method such as an injection molding method, an extrusion molding method, a blow molding method and a compression molding method can be adopted.

In the production of containers such as films, sheets, bottles, trays, etc., in addition to a molded product made of a single layer of resin, a multilayered product of another resin may be used. As the mating resin in the case of laminating, it is often carried out particularly for the purpose of imparting gas barrier properties, so that EVOH, nylon-6, nylon-
Polyamide resins such as 6,6 and vinylidene chloride resins are often used. Of course, normal thermoplastic resins other than the above, such as polycarbonate, vinyl chloride resin, acrylic resin, styrene resin, vinyl ester resin,
In addition to the polyester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene, and chlorinated polypropylene, the above-mentioned polyolefin resin may be used at all.

The layer structure of the molded article composed of the composition of the present invention is A (A ₁ , A ₂ , etc.), and the other resin layer mainly composed of a gas barrier resin is B (B ₁ , B 2). ₂ , etc.), when the adhesive layer provided as needed is C, if it is a film, a sheet, a bottle, etc., not only a two-layer structure of A / B,
A / B / A, B / A / B, B 1 / B 2 / A, B / A 1 /
A ₂ , A / B / A / B / A, A ₂ / A ₁ / B / A ₁ / A
₂ , A / C / B, A / C / B / C / A, B / C / A / C
/ B, A / C / B / C / A / C / B / C / A. When a polyolefin resin containing scrap is used as the polyolefin resin composition of the present invention constituting the multilayer laminate, it is preferably used as an outer layer or an intermediate layer of the laminate as a so-called scrap return layer. As an example of such a layer structure, when the virgin polyolefin resin layer of the present invention is A _V and the scrap-containing polyolefin resin layer is A _D , the structure is A _D (outer layer) / A _V (inner layer). You can also.
When the glossy resin (including the resin whose gloss has been lost) layer is E, E / A _V / E, E / A _D / A _V , E / A _D / A _V /
A glossy bottle having a layer structure such as E, E / A _D / A _V / A _D / E can also be used. The molded product after melt molding is subjected to heat treatment, cooling treatment, rolling treatment, uniaxial or biaxial stretching treatment, printing treatment, dry laminating treatment, solution or melt coating treatment, bag making processing, deep squeezing processing, box processing, tube as necessary Processing, split processing, and the like can be performed.

[0015]

In the resin composition of the present invention, by blending a very small amount of hydrotalcites, a polyolefin resin containing a nitrogen-containing antistatic agent, which is liable to yellow during melt molding, can be used at the time of melt molding. Yellowing due to heating can be effectively suppressed. In particular, in high-speed molding in which the temperature of the resin during melt molding is higher than 220 ° C., yellowing due to heating is remarkably observed, but the present invention suppresses yellowing during such high-temperature high-speed molding. It has a very remarkable effect. Therefore, the present invention is extremely useful for preventing a change in hue of a light-colored container mainly composed of a white pigment. Also, the present invention
Even in the case of a dark-colored container, it is useful for preventing a subtle change in hue and color unevenness. That is, the present invention not only prevents a decrease in the commercial value of the obtained polyolefin resin molded product itself, but also enables reuse of molding waste and defective products generated at the time of molding and recycled scrap as a resin raw material. It is of very high practical value. The molded product obtained from the polyolefin resin composition of the present invention is widely used as various containers such as bottles and trays, packaging films, sheets, various equipment parts and the like in the field of food packaging.

[0016]

EXAMPLES Next, the present invention will be further described with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. Hereinafter, the mixing ratio of each component means the mixing ratio by weight unless otherwise specified. (Yellowing prevention effect 1) Mel Flo as base resin
w Rate (MFR) 0.36 g / 10 min, density 0.
When a high-density polyethylene of 958 g / cm ³ (hues before the test: L83, a-0.8, b-0.9) was used and pelletized repeatedly at a predetermined resin temperature using a 40 mm extruder. Was observed. In this base resin, 500 ppm of a normal phosphorus-based antioxidant was used as an antioxidant, and N, N-bis (2
-Hydroxyethyl) alkylamine (1000 ppm) was added in advance, and hydrotalcite (manufactured by Kyowa Chemical Industry Co., Ltd .: DH) was further added as a neutralizing agent (hydrochloric acid absorbent).
T-4A), calcium stearate (St-Ca) and the like were added in various amounts and evaluated. Evaluation of the properties was performed using a Hunter color difference meter (manufactured by Kurabo Industries, color 71
Using a 0-color difference meter), the pellet was filled in a Petri dish having a diameter of about 10 cm and a depth of about 3 cm, and was placed on a measuring table, and evaluated by the following three measured values. L: Indicates the degree of whiteness. Larger numbers indicate white. a: Shows red and green hues. A larger absolute value of the number indicates a stronger reddish color. b: Shows yellow and blue hues. Larger numbers indicate stronger yellow. Table 1 shows the additive formulation and hue change of each resin composition.

[0017]

[Table 1]

According to the results, when the neutralizing agent was not added or when calcium stearate (St-Ca), which has been generally used conventionally, was added, the change in hue, particularly the change in the b value, was large (comparative to the comparative example). Examples 1 to 3) and addition of a considerably excessive amount (Comparative Example 4), although the change in hue is slightly suppressed, does not reach a practical level. In addition, when the amount of St-Ca increases, the resin tends to slip when biting, and the molding conditions tend to be unstable, and bleeding increases and the surface of the molded product tends to become sticky. On the other hand, when the hydrotalcite of the present invention was added, a remarkable effect on the change in hue was recognized even with a small addition of about 100 ppm. In addition, conventional St-Ca
When used in combination with a neutralizing agent such as the above, it was more effective in suppressing hue change during high-temperature processing. According to the present invention, since addition of a small amount of hydrotalcite is sufficient, there is no change in appearance such as surface gloss of the molded product, and there is a remarkable improvement effect from the economical point of view.

(Yellowing prevention effect 2) MF as base resin
R: 0.36 g / 10 min, high-density polyethylene having a density of 0.958 g / cm ³ was used, and titanium oxide (titanium PIG) was added about 20 times as a white pigment so that the final amount of addition was 1% by weight. The master batch was diluted, and each of the additive formulations shown in Table 2 was used. From each resin composition, the outer layer contains 50% regrind such as burrs and adjusting bottles, the inner layer is made of virgin resin, and the outer layer /
The inner layer has a layer ratio of 4: 1 and two types of two layers, a body diameter of 70 mm,
A round bottle having a height of 180 mm, a basis weight of 43 g and an internal volume of 500 ml was prepared by direct blow at a molding speed of 55 tubes per minute and a resin temperature of 238 ° C. during molding. Samples were taken under conditions where the outer layer contained a regrind resin that had undergone at least 5 molding cycles, and their mutual color difference (ΔE) was evaluated using an all virgin bottle as a control. In addition, during the bottle molding, a frame treatment is performed in-line so that the wetting index becomes 52 dynes / cm, and the surface resistivity of the bottle side wall 24 hours after the molding is measured, while the dirt chamber test (DCT). Was used to evaluate the antistatic property. Table 2 shows the results.

[0020]

[Table 2]

* In Table 2, the additives represented by the abbreviations are as follows. HT: Hydrotalcite [Kyowa Chemical Industry Co., Ltd., D
HT-4A] EA: N, N-bis (2-hydroxyethyl) alkylamine AO: Phosphorus antioxidant SC: Calcium stearate (St-Ca) MG: Monoglycerin stearate ** In addition, DCT has 5 steps. It is a value obtained by evaluation, and 4 or more means that there is practicality.

From the actual bottle molding examples of Comparative Examples 5 and 6,
As an effect of using N, N-bis (2-hydroxyethyl) alkylamine as an antistatic agent, it can be seen that the antistatic ability can be stably exhibited by relatively light flame treatment in-line. However, when only calcium stearate was used as the neutralizing agent, the discoloration of the container was remarkable and the practicality was poor (Comparative Example 6). In addition, in the case of monoglycerin stearate, which is a general nonionic antistatic agent, the discoloration of the resin at the time of molding hardly occurs, but the compatibility with the resin and the difference in the bleeding speed reflect the antistatic ability. Is late, and the bottle is contaminated when being conveyed in the bottle line (Comparative Example 7).
On the other hand, when hydrotalcite (DHT-4A manufactured by Kyowa Chemical Industry Co., Ltd.) is used as the neutralizing agent, the change in hue is maintained at almost the minimum level without affecting the expression of antistatic ability. be able to. Looking at the surface specific resistance value, the addition of hydrotalcite tends to slightly decrease the antistatic ability, but the addition amount of about 500 ppm hardly affects practical performance (the present invention 9). When calcium stearate is also used in combination with the neutralizing agent, the change in hue is small, the antistatic ability can be maintained high, the rise in resin temperature during molding can be suppressed, and the load during molding can be reduced (the present invention 10). ).

Claims (11)

[Claims] 1. A polyolefin resin composition comprising (A) a polyolefin resin, (B) a nitrogen-containing antistatic agent, and (C) a hydrotalcite represented by the following general formula (1). Stuff. M _x Al _y (OH) _{2x + 3y-2z} (A) _z · aH ₂ O (1) (M is Mg, Ca or Zn, A is CO ₃ or HPO ₄ ,
x, y, z are positive numbers, a is 0 or a positive number) 2. The polyolefin resin composition according to claim 1, further comprising (D) a metal salt of a higher fatty acid. 3. The polyolefin resin composition according to claim 1, wherein the polyolefin resin (A) contains a used polyolefin resin. 4. The method according to claim 1, wherein the nitrogen-containing antistatic agent (B) is a hindered amine antistatic agent.
The polyolefin resin composition according to any one of the above. 5. The polyolefin resin composition according to claim 1, wherein the nitrogen-containing antistatic agent (B) is an alkylethanolamine. 6. The hydrotalcite represented by the general formula (1), wherein M is Mg and A is CO _3. The polyolefin resin composition according to claim 1 or 2. 7. The hydrotalcites (C) are added in an amount of 0.005 to 100 parts by weight of the polyolefin resin (A).
7. The composition according to claim 1, which contains 0.15 parts by weight.
The polyolefin resin composition according to any one of the above. 8. A method for producing a polyolefin molded product, comprising melt-molding the polyolefin resin composition according to any one of claims 1 to 7. 9. The method according to claim 8, wherein the molded product is a container. 10. A polyolefin container produced from the polyolefin resin composition according to any one of claims 1 to 7. 11. A container comprising a multilayer laminate, wherein at least one layer contains the polyolefin resin composition according to any one of claims 1 to 7 as a raw material. 5. The polyolefin container according to 1.