Uncolored resin molding

Abstract

To provide an uncolored resin molding composed of an ethylene-based resin composition, which effectively prevents yellowing due to long-term storage.SOLUTION: The present invention provides an uncolored resin molding composed of an ethylene-based resin composition, wherein the resin composition comprises: a phenolic antioxidant (A) having a melting point of 200°C or less; a phosphorus antioxidant (B) having a melting point of 200°C or more; and a benzophenone-based ultraviolet absorber (C).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin molded article made of an uncolored ethylene-based resin composition. [Background technology]

[0002] Plastics are widely used in various fields because they are easy to mold and can be easily shaped into various shapes. In resin molded products made of such plastics, antioxidants such as phosphorus-based antioxidants and phenol-based antioxidants are usually blended to prevent oxidation of the resin (Patent Document 1).

[0003] Incidentally, the above-mentioned resin molded products are often colored in various colors by blending colorants from the viewpoints of appearance, design, light shielding, etc., but some are uncolored depending on the application. For example, in the case of resin molded products used as packaging materials such as caps and spouts, depending on the substance to be packaged (e.g., medicines), contact with colorants may be undesirable, and in such cases, uncolored products that do not contain colorants are used. In addition, in recent years, recyclability of resins has been required from the viewpoints of resource conservation and effective use of resources, and from the viewpoint of such recyclability, uncolored products that do not contain colorants are sometimes preferred for use.

[0004] However, there was an unexpected problem that uncolored resin molded products, particularly resin molded products obtained using ethylene-based resins, undergo color change (yellowing) over long-term storage, impairing their commercial value. In particular, uncolored products such as caps and spouts, which may be sterilized with ultraviolet light during the filling process of the content liquid, may undergo yellowing and deterioration over long-term storage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2002-531622 Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an uncolored resin molded article made of an ethylene-based resin composition which is effectively prevented from yellowing due to long-term storage. [Means for solving the problem]

[0007] The present inventors conducted many experiments and studies on yellowing of resin molded articles made of ethylene-based resin compositions during long-term storage, and as a result, discovered that an antioxidant used to prevent deterioration due to thermal history during molding has a significant effect on deterioration during long-term storage, and that by combining this additive (antioxidant) with a specific ultraviolet absorber, it is possible to effectively avoid deterioration due to thermal history during molding as well as deterioration during long-term storage, and thus completed the present invention.

[0008] That is, according to the present invention, in an uncolored resin molded article made of an ethylene-based resin composition, The resin composition provides an uncolored resin molded product, which is characterized in that it contains a phenol-based antioxidant (A) having a melting point of 200°C or lower, a phosphorus-based antioxidant (B) having a melting point of 200°C or higher, and a benzophenone-based ultraviolet absorber (C).

[0009] In the uncolored resin molded product of the present invention, (1) The ethylene-based resin is a high-density polyethylene; (2) containing 0.01 to 0.2 parts by mass of the phenol-based antioxidant (A), 0.01 to 0.2 parts by mass of the phosphorus-based antioxidant (B), and 0.01 to 0.1 parts by mass of the benzophenone-based ultraviolet absorber (C) per 100 parts by mass of the ethylene-based resin; (3) It is a cap or spout; is preferred. Effect of the Invention

[0010] The uncolored resin molded article of the present invention exhibits excellent weather resistance, and color change (yellowing) is effectively prevented even when it is assumed that it will be stored for a long period of time, for example, more than one year, in a warehouse, etc. The weather resistance during such long-term storage can be evaluated by an accelerated deterioration test by ultraviolet irradiation using a UV germicidal lamp, as shown in the examples described later. Furthermore, the uncolored resin molded product is effectively prevented from thermal deterioration (browning) during thermoforming. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The uncolored resin molded article of the present invention is obtained by molding an ethylene-based resin composition, but this resin composition does not contain a colorant and is uncolored. That is, since it is uncolored, it has the property of easily transmitting light. Such light transmittance has a significant effect on the weather resistance of the molded article, leading to a decrease in weather resistance, but in the present invention, the decrease in weather resistance due to the uncolored state is effectively suppressed.

[0012] In the present invention, the fact that no coloring agent is blended and that the product is uncolored means that the original color of the resin constituting the molded product is expressed. For example, various coloring pigments and dyes are used as coloring agents, and additives such as lubricants, surfactants, and fillers that are usually blended into resin compositions have color. That is, in the present invention, the fact that the product is uncolored means that even if these additives are blended, they are not blended in an amount that would exert a hiding power. For example, the resin molded product of the present invention has a total light transmittance of 90% or more for visible light, and is cloudy, translucent, or opaque.

[0013] <Ethylene-based resin composition> In the present invention, the resin composition used to form the uncolored molded article contains an ethylene-based resin as a resin component.

[0014] As the ethylene-based resin, not only polyethylene but also a copolymer of ethylene with a small amount of α-olefin (e.g., propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc.) can be used. For example, low-density polyethylene, high-density polyethylene, linear low-density polyethylene, etc. can be used.

[0015] In the present invention, in order to make the most of the advantage of excellent weather resistance over a long period of time, high-density polyethylene having excellent mechanical strength and abrasion resistance capable of withstanding long-term use, particularly a polyethylene having a density of 0.942 g / cm3, is used. 3 Above 0.950~0.970g / cm 3 High density polyethylene is most preferably used.

[0016] The ethylene resins used have an MFR (melt flow rate) that corresponds to the molding method used to manufacture the molded product, such as injection molding, compression molding, extrusion molding, etc. For example, in the case of the high-density polyethylene, injection molding grades generally have an MFR of 2.0 to 12.0 g / 10 min (190° C.), compression molding grades generally have an MFR of 0.5 to 10.0 g / 10 min (190° C.), and extrusion molding grades generally have an MFR of 0.5 g / 10 min (190° C.) or less.

[0017] The ethylene-based resin composition used in the present invention may be blended with a small amount of other resin components (for example, olefin-based resins such as polypropylene) as long as the above-mentioned properties of the ethylene-based resin are not impaired.

[0018] In the present invention, in order to prevent deterioration during molding, a phenol-based antioxidant (A) and a phosphorus-based antioxidant (B) are blended into the ethylene-based resin composition, but in addition to these, it is necessary to blend a benzophenone-based ultraviolet absorber (C). That is, when no antioxidant is used, weather resistance can be ensured over a long period of time without blending a benzophenone-based ultraviolet absorber (C). This suggests that the deterioration of weather resistance, that is, the color change (yellowing) of the molded product that occurs during long-term storage, is caused by the deterioration of the antioxidant due to light. Therefore, in order to ensure weather resistance over a long period of time, it is sufficient not to blend an antioxidant, but in that case, deterioration occurs during molding of the ethylene-based resin composition, and browning, so-called tanning, occurs. For this reason, blending an antioxidant is essential, and further, blending a benzophenone-based ultraviolet absorber (C) is essential to prevent the deterioration of weather resistance caused by blending an antioxidant.

[0019] Phenolic antioxidants (A); In the present invention, the phenol-based antioxidant (A) used has a melting point of 200° C. or less, preferably 100° C. or less. Such a low-melting-point phenol-based antioxidant (A) has a function of preventing oxidation deterioration of ethylene-based resins due to heat history in a relatively low temperature range during molding, and by using it in combination with a phosphorus-based antioxidant (B) described below, it becomes possible to effectively avoid the deterioration called discoloration (browning) of ethylene-based resins that occurs during molding. For example, when a phenol-based antioxidant with a melting point higher than 200° C. is used, discoloration that occurs during molding cannot be sufficiently prevented.

[0020] As the above-mentioned low melting point phenol-based antioxidant (A), various substances are known, but hindered phenol-based antioxidants are preferably used because of their particularly strong antioxidant function. Hindered phenol-based antioxidants are phenolic compounds having substituents with high steric hindrance (such as tertiary butyl groups) at two positions adjacent to the phenolic OH group, and the following are representative examples. 2,6-Di-tert-butylphenol 2,6-Di-tert-butyl-p-cresol 2,6-Di-tert-butyl-4-ethylphenol 2,6-Di-tert-butyl-4-methoxyphenol 4,6-Di-tert-butylresorcinol 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid Octadecyl (Irganox 1076 (registered trademark)) 4-[[4,6-bis(n-octylthio)-1,3,5-triazin-2-yl ] Amino]-2,6-di-tert-butylphenol Stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

[0021] The low melting point phenolic antioxidant (A) is preferably used in an amount of 0.01 to 0.2 parts by mass, particularly 0.05 to 0.1 parts by mass, per 100 parts by mass of the ethylene resin. When this amount is small or large, the effect of preventing scorching during thermoforming may be insufficient, or long-term weather resistance may be insufficient.

[0022] Phosphorus-based antioxidants (B); The phosphorus-based antioxidant (B) used in the present invention has the function of preventing deterioration of the ethylene-based resin in a relatively high temperature range, and by using it in combination with the above-mentioned low-melting-point phenol-based antioxidant (A), it becomes possible to reliably avoid the deterioration called discoloration (browning) of the ethylene-based resin that occurs during molding.

[0023] In addition, the phosphorus-based antioxidant (B) used in the present invention must have a melting point of 200°C or higher. That is, when a phosphorus-based antioxidant with a low melting point is used in combination with the above-mentioned low-melting-point phenol-based antioxidant (A), even if the discoloration of the ethylene-based resin occurring during molding can be prevented, long-term weather resistance cannot be ensured and yellowing may occur in a short period of time. However, when a phosphorus-based antioxidant (B) with a melting point of 200°C or higher is used in combination with a low-melting-point phenol-based antioxidant (A), discoloration of the ethylene-based resin occurring during molding can be reliably prevented, and at the same time, long-term weather resistance can be ensured, and for example, even if it is stored in a warehouse or the like for more than one year, yellowing will not occur.

[0024] Incidentally, the present inventors presume the above-mentioned weather resistance as follows. That is, in a molded product of a colored ethylene resin, light (ultraviolet rays) does not pass through but is absorbed by the coloring agent, so the problem of discoloration due to ultraviolet rays can be ignored. On the other hand, in a molded product of an uncolored ethylene resin, not only is light (ultraviolet rays) not absorbed, but it is transparent or translucent, and color changes caused by deterioration of the resin caused by ultraviolet rays become significant, and there is a risk that it will appear as yellowing when stored for a long period of time of one year or more. However, in the present invention, yellowing during long-term storage can be effectively avoided by using a phosphorus-based antioxidant (B) having a melting point of 200°C or more. In other words, it is considered that the presence of a phosphorus-based antioxidant used to prevent scorching during molding has a significant effect on yellowing, and by using such a phosphorus-based antioxidant (B) having a high melting point of 200°C or more, the stability of the phosphorus-based antioxidant (B) is increased, and as a result, it is possible to prevent yellowing during long-term storage, and it is considered that long-term weather resistance can be ensured.

[0025] In the present invention, the high melting point phosphorus-based antioxidant (B) is typically a phosphite-based or phosphate-based compound.

[0026] An example of the phosphite compound is 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (melting point: 234 to 240° C.) represented by the following formula. This phosphite compound is commercially available from ADEKA CORPORATION under the trade name Adeka STAB PEP-36. [ka]

[0027] In addition, many high melting point phosphate compounds are known, and are disclosed, for example, in Japanese Patent No. 5140560. Specifically, phosphates represented by the following general formula (1) or (2) are preferably used.

[0028] A phosphate compound represented by the general formula (1): [ka] In the above formula, R 1 represents a direct bond, sulfur, or an alkylene or alkylidene group having 1 to 9 carbon atoms; R 2 and R 3 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, M is an alkali metal such as Na, K, or Li (especially Na or K), or Ca, Mg , alkaline earth metals such as Sr, Zn, Cd, etc. n is the valence of M.

[0029] Specific examples of the above phosphate salts are as follows: Sodium 2,2'-methylene-bis-(4,6-di-t-butylphenyl) phosphate, Sodium 2,2'-ethylidene-bis-(4,6-di-t-butylphenyl) phosphate, Na-2,2'-ethylidene-bis-(4-i-propyl-6-t-butylphenyl) phosphate, Na-2,2'-butylidene-bis-(4,6-dimethylphenyl) phosphate, Na-2,2'-butylidene-bis-(4,6-di-t-butylphenyl) phosphate, Na-2,2'-t-octylmethylene-bis-(4,6-methylphenyl) phosphate, Na-2,2'-t-octylmethylene-bis-(4,6-di-t-butylphenyl) phosphate, Na-2,2'-methylene-bis-(4- methyl-6-t-butylphenyl) phosphate, Na-2,2'-methylene-bis-(4-ethyl-6-t-butylphenyl) phosphate, Na (4,4'-dimethyl-6,6'-di-t-butyl-2,2'-biphenyl) phosphate, Na-2,2'-ethylidene-bis-(4-s-butyl-6-t-butylphenyl) phosphate, Na-2,2'-methylene-bis-(4,6-di-methylphenyl) phosphate, Na-2,2'-methylene-bis-(4,6-di-ethylphenyl) phosphate, etc.

[0030] A phosphate compound represented by the general formula (2): [ka] In the above formula, R 1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 2 and R 3 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, M is a metal atom of group III or IV of the periodic table (e.g., Al, Sn, Pb, Ti, Zr, preferably Al), X represents HO- when M represents a metal atom of Group III of the periodic table; When referring to a metal atom of Group IV of the periodic table, O= or (HO)2-.

[0031] Specific examples of the above phosphate salts are as follows: Hydroxyaluminum bis[2,2'-methylene-bis(4,6-dimethylphenyl)phosphate], Hydroxyaluminum bis[2,2'-ethylidene-bis(4,6-dimethylphenyl)phosphate], Hydroxyaluminum bis[2,2'-methylene-bis(4,6-diethylphenyl)phosphate], Hydroxyaluminum bis[2,2'-ethylidene-bis(4,6-diethylphenyl)phosphate], Hydroxyaluminum bis[2,2'-methylene-bis(4,6-di-t-butylphenyl)phosphate], Hydroxyaluminum bis[2,2'-ethylidene-bis(4,6-di-t-butylphenyl)phosphate], Hydroxyaluminum bis[2,2'-methylene-bis(4-methyl-6-t-butylphenyl)phosphate], Hydroxyaluminum bis[2,2'-ethylidene-bis(4-methyl-6-t-butylphenyl)phosphate], Hydroxyaluminum bis[2,2'-methylene-bis(4-ethyl-6-t-butylphenyl)phosphate], Hydroxyaluminum bis[2,2'-ethylidene-bis(4-ethyl-6-t-butylphenyl)phosphate], Hydroxyaluminum bis[2,2'-methylene-bis(4-i-propyl-6-t-butylphenyl)phosphate], Hydroxyaluminum bis[2,2'-ethylidene-bis(4-i-propyl-6-t-butylphenyl)phosphate], etc.

[0032] The above-mentioned various high melting point phosphorus-based antioxidants (B) can be used either alone or in combination of two or more.

[0033] In the present invention, such a high melting point phosphorus-based antioxidant is preferably used in an amount of 0.01 to 0.2 parts by mass, particularly 0.02 to 0.1 parts by mass, per 100 parts by mass of the above-mentioned ethylene-based resin. If this amount is small, the effect of preventing scorching during thermoforming tends to be insufficient, and if used in a large amount, the long-term weather resistance tends to be insufficient.

[0034] Benzophenone-based ultraviolet absorbers (C); In the present invention, a benzophenone-based ultraviolet absorber (C) is used together with the above-mentioned phenol-based antioxidant (A) and phosphorus-based antioxidant (B). That is, the incorporation of this benzophenone-based ultraviolet absorber (C) can effectively prevent the deterioration of long-term weather resistance (i.e., yellowing that occurs during long-term storage) that would be caused by the deterioration of the antioxidants (A) and (B) that occurs when the composition is uncolored without the incorporation of colorants, etc.

[0035] Such benzophenone-based ultraviolet absorbents have the advantage that they are hygienic and can be used in food applications. Examples thereof include the following. 2-Hydroxy-4-methoxy-benzophenone 2-Hydroxy-4-n-octoxybenzophenone In the present invention, 2-hydroxy-4-n-octoxybenzophenone is particularly suitable because it has excellent compatibility with ethylene resins, exhibits high absorption in the short-wavelength ultraviolet region, and can effectively suppress the deterioration of the antioxidants (A) and (B) even during ultraviolet sterilization. This benzophenone ultraviolet absorber is represented by the following formula and is commercially available from ADEKA CORPORATION under the product name Adeka STAB 1413. [ka]

[0036] In the present invention, such a benzophenone-based ultraviolet absorber (C) is preferably used in an amount of 0.01 to 0.1 parts by mass, particularly 0.02 to 0.08 parts by mass, per 100 parts by mass of the above-mentioned ethylene-based resin. If this amount is small, the long-term weather resistance may be insufficient, and if used in a large amount, the effect of preventing scorching during thermoforming may be reduced.

[0037] <Production and use of uncolored resin molded products> The uncolored resin molded article of the present invention can be obtained by melt-kneading predetermined amounts of the above-mentioned ethylene-based resin, the low-melting-point phenol-based antioxidant (A), the high-melting-point phosphorus-based antioxidant (B), the benzophenone-based ultraviolet absorber (C), and additives such as lubricants which are blended as necessary for purposes other than coloring, and subjecting the resulting resin composition to a known molding means, for example, extrusion molding, injection molding, compression molding, or the like.

[0038] In addition, when producing a resin molded product as described above, a master batch in which a large amount of a phenol-based antioxidant (A), a phosphorus-based antioxidant (B), a benzophenone-based ultraviolet absorber (C), etc. are blended with an ethylene-based resin may be produced and stored in advance, and the master batch may be diluted with an ethylene-based resin, etc. to prepare an ethylene-based resin composition, and then a predetermined molding method may be carried out. In such a case, the master batch may be stored for a long period of time. In order to ensure weather resistance at such a master batch stage and to reliably prevent yellowing, it is preferable to set the mass ratio (B / C) of the phosphorus-based antioxidant (B) and the benzophenone-based ultraviolet absorber (C) to be 1 to 2. This effectively prevents the deterioration of the phosphorus-based antioxidant (B) during storage of the master batch, and effectively prevents the master batch from yellowing.

[0039] As already mentioned, the uncolored ethylene resin molded article produced as described above is not colored, is transparent or translucent, and has high light transmittance. Such molded articles are particularly suitable as caps or spouts used in packaging materials for lactic acid beverages or medicines, which should not come into contact with colorants. Since such molded articles do not contain colorants, they are also suitable for recycling. In addition, as can be seen from the results of accelerated deterioration tests using ultraviolet light irradiation for the evaluation of long-term weather resistance in the examples described later, deterioration due to sterilization treatment using ultraviolet light irradiation is also effectively avoided. EXAMPLES

[0040] The excellent effects of the present invention will be illustrated by the following experimental examples.

[0041] <Various materials used in the experiment> Ethylene-based resins; High Density Polyethylene (HDPE) Density: 0.964g / cm 3 MFR(190℃):5.2g / 10min Phenolic antioxidants (A); A1: (Irganox 1076) 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propion Octadecyl Acetate Melting point: 50~55℃

[0042] Phosphorus-based antioxidants (B); B1 (BASF Irgafos168) Tris(2,4-di-tert-butylphenyl)phosphite Melting point: 183-186℃ B2 (BASF Irgafos126) 3,9-bis(2,4-di-tert-butylphenyl)-2, 4,8,10-tetraoxa-3,9- diphosphaspiro[5.5]undecane Melting point: 160℃ B3 (ADEKA stub 2112) Tris(2,4-di-tert-butylphenyl)phosphite Melting point: 180~190℃ B4 (ADEKA Adeka STAB PEP-36) 3,9-Bis(2,6-di-tert-butyl-4-methylphenoxy)- 2,4,8,10-Tetraoxa-3,9-diphosphaspiro[5.5]undecane Melting point: 234~240℃

[0043] Benzophenone antioxidants (C); C1 (ADEKA stub 1413) 2-Hydroxy-4-n-octoxybenzophenone Melting point: 47~49℃

[0044] The various characteristics obtained in each experimental example were measured by the following methods.

[0045] Scorch test; 5 g of sample resin pellets were placed in an aluminum cup, and heated at 200° C. for 60 minutes. The browning (scorching resistance) was evaluated by visual inspection. The evaluation criteria were as follows: 〇: No change △: Some browning ×: Browning observed

[0046] Yellowing (accelerated aging test); Using a UV germicidal lamp, the cumulative light intensity is 400,000mW·sec / cm 2 The sample resin pellets were irradiated with ultraviolet light at 40°C, and the yellowing was measured by color difference (ΔE) using a colorimeter to evaluate long-term weather resistance. The evaluation criteria are as follows: ◯: ΔE is 1.5 or less. △: ΔE is 1.6 to 3.0. ×: ΔE exceeds 3.0.

[0047] <Experiment 1~Experiment 15> Each component was mixed with 100 parts by mass of ethylene resin in the amount ratio shown in Table 1, melt-kneaded at a temperature of 190°C, melt-extruded, and prepared into resin pellets for testing, which were then subjected to various measurements. The results are also shown in Table 1.

[0048] [Table 1]

Claims

1. In an uncolored resin molded product made of an ethylene-based resin composition, The resin composition contains a phenol-based antioxidant (A) having a melting point of 200°C or lower, a phosphorus-based antioxidant (B) having a melting point of 200°C or higher, and a benzophenone-based ultraviolet absorber (C).

2. 2. The uncolored resin molded product according to claim 1, wherein said ethylene resin is a high density polyethylene.

3. 2. The uncolored resin molded product according to claim 1, comprising, per 100 parts by mass of the ethylene-based resin, 0.01 to 0.2 parts by mass of the phenol-based antioxidant (A), 0.01 to 0.2 parts by mass of the phosphorus-based antioxidant (B), and 0.01 to 0.1 parts by mass of the benzophenone-based ultraviolet absorber (C).

4. 4. The uncolored resin molded article according to claim 1, which is a cap or a spout.

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