JPS6226663B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the prevention and/or suppression of discoloration of polyolefins protected by antioxidants, and to materials and methods therefor. Various polyolefins are commercially available and are used for many purposes. The polyolefins most commonly used in various commercial products are polypropylene, high density polyethylene, low density polyethylene, linear low density polyethylene, and polybutylene. Products based on such polyolefins are manufactured by extrusion molding, injection molding, blow molding, film extrusion, and other resin processing methods. During such processing, polyolefins are exposed to elevated temperatures. The elevated temperature here is a temperature high enough to affect the stiffness of the polyolefin, but generally below the decomposition point of the polymer. Some examples of commercial polyolefins include: 1 Polypropyne, such as Prpfax 6501 (Trademark, Hercules Powder, Inc.), Dypro (Trademark, Arco Chemical) company (ARCO)
Chemical Co.]; 2 High-density polyethylene, such as Marlex (trademark, Phillips Chemical Co.); 3 Low-density polyethylene, such as Norchem NPE420 (trademark, Northern Petrochemicals Co.) (Northern Petrochemicals
4 Linear low-density polyethylene (LLDPE), such as Dowlex 2252 [trademark, Dow
Dow Chemical Co., LPX-2
and LPX-7 [Trademark, Exxon
Corp.] and Union Carbide's UCC-1055 (trademark); 5 Witco Chemical
Co.) polybutylene. The polyolefins described above are used to make soft and hard plastic products such as toys, office supplies, containers, household products, cable coverings, films, textiles and other industrial products. The polyolefins described above usually require protection with antioxidants to avoid molecular degradation or other degradation that occurs when exposed to air and elevated temperatures. For example, PROFAX 6501 polypropylene without added stabilizers "breaks down" after only about 3 to 4 hours in a 150°C oven aging test.
wake up However, any known commercially used antioxidant may be added to Profax 6501.
When added to polypropylene, the life of this polyolefin is significantly extended. For example, 1,3,5-trimethyl-2, commercially available from Ethy Corporation under the trademark Ethanox 330 antioxidant,
4,6-tris(3',5'-di-t-butyl-4'-
The combination of hydroxybenzyl)benzene and polypropylene provides an oven aging test life of more than 1000 hours at 150°C. The history of polyolefin production includes advances in catalyst systems and post-polymerization recovery techniques that affect the purity of bulk polyolefins. since the 1960s
Through the 1970s, slurry processes, such as those developed by Phillips Petroleum Co., were used. This slurry method required a catalyst separation step. Although this process is more effective for catalyst recovery than current methods, it is extremely expensive in terms of handling, catalyst loss, and solvent costs for separation. Chemical
Economics Handbook, SRI International,
Plastics and Resins, 580.1342A (August 1981) describes this type of method and compares it with newer methods. Also, the
On page 282 of the Encyclopedia of Polymer Technology volume (1981 edition) a comparison is made between the Phillips slurry process and the (relatively) new Ziegler process. Post-polymerization purification of propylene is discussed on page 605. It is stated therein that metal residues remain within the polymer product. Another example of the Phillips slurry process is U.S. Pat. No. 2,825,721 (1958) by Hogen et al.
year). Further, Philips U.S. Pat. No. 3,502,634 (1970) by Stedefeder et al. discloses a slurry method using 5,000 parts of methanol washing solution for 1.25 parts of titanium trichloride catalyst. . Phillips U.S. Pat. No. 3,922,249 (1975) describes N, N, used as an antistatic agent.
It has been disclosed that -bis(hydroxyalkyl)-N-alkylamines cause discoloration of polyolefins produced by a slurry process. These amines are manufactured by, for example, Armor Industrial Chemical Co.
Armostat from Chemical Co.
N,N-bis(2-hydroxyethyl)-N-octadecylamine named 310 is included. Discoloration by the listed amines is known and
The method described in US Pat. No. 3,922,249 involves the use of certain phosphites to prevent discoloration caused by antistatic agents. Most mass-produced polyolefins, including high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polybutylene, polypropylene, etc., are currently manufactured using metal-containing catalysts, and this process eliminates the trace amounts of catalytic metals being recovered and is incorporated into the polymer. remain in the Polyolefins are made by methods involving a variety of metal-containing catalyst systems. Therefore, these polyolefins contain significant amounts of various metals. These metals have been found to affect either the polyolefin substrate or the phenolic antioxidant by some mechanism, causing or permitting a color change.
Therefore, it is theorized that the coloring inhibitor of the present invention is capable of binding to metal contaminants like a chelating agent. The metal analysis results for the three polyolefin samples are shown in Table A. On the other hand, when the polyolefin base contains almost no impurities, the discoloration caused by the phenolic antioxidant is small, and the effect of adding the anti-discoloration agent of the present invention is not as strong or long-lasting as when it contains many metal impurities. do not have. In fact, the discoloration after long-term oven aging may be worse with the inhibitor added than without it. [Table] Examples of other metals with a content of less than 1 ppm are Cr, Zn,
These are Cu, Co, Cd, Mn, Mo, Na, Ni, and Fe. Depending on the catalyst base and the post-polymerization recovery technique, higher amounts of these or other metals may be present. Although not all of the effects of catalytic trace metals in polymers are known, most polymers currently produced, especially commodity grades and relatively "dirty" mass-produced polymers, are coloration by adding an effective amount of antioxidants of the type. Without adding antioxidants,
Of course, the lifespan of polymer products will be extremely shortened. Coloration is an important issue for polyolefin and antioxidant combinations. Although we may think of this problem as merely an aesthetic one, it is far from being such a problem; it is a very important one. In order for products made from antioxidant-protected polyolefins to be commercially viable, they often start out white or transparent and must remain that color. The problem of discoloration is of particular importance for containers and other products where a standard white color is required for the manufacture of the final product and/or before conversion to another color. The combination of polyolefin and antioxidant includes
There are some combinations in which the degree of discoloration is more severe than in other combinations. Additionally, the degree of initial discoloration and discoloration over time depends not only on the amount of antioxidant, but also on the specific type of polyolefin used, the number of extrusion cycles, the severity of the processing, and the content of contaminants. It also changes depending on. The present invention relates to a composition comprising a large proportion of a polyolefin and a small proportion of an antioxidant that protects the polyolefin, the polyolefin being combined with a phenolic antioxidant contained in the polyolefin to prevent discoloration. A small amount of catalytic metal impurities and (a) pentaerythritol and approx.
Polyol reaction product with propylene oxide having a hydroxy value of 500, and (b) structure: (wherein R and R' are H or alkyl,
x is greater than 0 and y is between 0 and 2)
a compound selected from the group consisting of polyhydroxy hydrocarbons having do. Given that some of these inhibitor compounds are the same as those known to cause yellowing and other discoloration of polyolefins produced in a manner that leaves the polymer in a substantially pure state, , the results of the present invention are completely unexpected. In addition, the present invention uses a phenolic antioxidant of about 1.0
and 0.025 to 1.0 parts by weight of a polyol reaction product of pentaerythritol and propylene oxide having a hydroxyl number of about 500, or a polyhydroxy hydrocarbon having the structure. The present invention also provides a method for preventing and/or inhibiting discoloration of an antioxidant-protected polyolefin contaminated with a catalyst, the method comprising: inhibiting and/or inhibiting discoloration of an antioxidant-protected polyolefin. It also relates to a method of mixing the polyolefin with an amount of a polyol reaction product of pentaerythritol and propylene oxide having a hydroxyl number of about 500, or a polyhydroxy hydrocarbon having the structure. The scope of the invention also includes products made using the compositions or methods of the invention. Firstly, the present invention provides 1,3,5-trimethyl-
2,4,6-tris(3',5'-di-t-butyl-
4'-Hydroxybenzyl)benzene to prevent or suppress yellowing of polyolefins that are otherwise prone to discoloration, the method comprises adding a portion of pentaerythritol and/or pentaerythritol to said polyolefin. and about
A polyol reaction product with propylene oxide having a hydroxyl number of 500 is added in an amount sufficient to prevent or inhibit discoloration of the protected polyolefin initially, over time, and upon exposure to elevated temperatures or air. It consists of things. The present invention encompasses polyolefin-antioxidant-additive compositions, antioxidant-additive compositions, and various inventive methods of component mixing and polyolefin protection. The antioxidant-additive composition of the present invention can be mixed into a polyolefin in the same manner as is known in the art for dispersing or mixing antioxidants into polyolefins. Alternatively, the antioxidant-protected polyolefin and the anti-tarnish compound of the present invention or mixtures thereof may be re-extruded together. Other commercially used antioxidants and polyolefins can also be used in the methods of the invention along with the compositions of the invention. By adding anti-tarnish or inhibiting amounts of the additive compounds of the present invention, the color of the antioxidant-protected polyolefin is not only improved initially, but also maintained well thereafter. Various antioxidants suitable for the present invention are known in the art and are used commercially, including 2,6-di-t-butyl-p-cresol, 1, 3,5-trimethyl-2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)benzene, tris(3,5-di-t-butyl-4-hydroxybenzyl) ) isocyanurate and tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. They are marketed as BHT (butylated hydroxytoluene - generic name) and are sold under the trademark Ethanox 330 by Esil Corporation, BF
BFGoodrich Chemical Company
It is sold by Ciba-Geigy Corp. under the trademark Goodrite 3114 (trademark) and by Ciba-Geigy Corp. under the trademark Irganox 1010. Other phenolic antioxidants include Ciba
Included are Geigy's Irganox 1076 trademark and ICI's Topanol CA™. Methods for making these antioxidants are well known in the art. For example, the second compound listed is Rocklin's US Patent No. 3,026,264.
No. 3,025,488 or Shin U.S. Pat. No. 3,025,488
It can be produced by the method described in any one of the specifications of the patent. Antioxidants that can be used in the present invention are the phenolic antioxidants mentioned above as well as other antioxidants suitable for protecting polyolefins. The meaning of the term polyolefin includes polypropylene, polyethylene (high density), low density polyethylene, linear low density polyethylene (often made from the main monomer and about 5-10% comonomer), polybutylene, polybutadiene, cis-
Homopolymers and copolymers including polybutadiene rubber, ethylene-propylene copolymers and ethylene-propylene-diene copolymers, such as ethylene-propylene-cyclopentandiene, ethylene-propylene-1,4-cyclooctadiene, and the like are included. Further, the polyolefin of the present invention is a polyolefin whose color is not changed by adding the inhibitor according to the present invention, but rather its color is improved. Polymers excluded from the scope of the invention therefore include:
Included are the ethylene/1-butene copolymers (polyethylene) described in and for example in Phillips US Pat. No. 3,922,249. It appears that these copolymers were made using the Phillips slurry, solvent recovery process, which removes virtually all catalyst residue (albeit at a slightly higher cost). A preferred embodiment of the present invention is a polyolefin containing catalyst residues as described above, which is protected from long-term gradual degradation due to oxidation by an antioxidant, and which is protected by the anti-tarnish/inhibitor compound of the present invention. It is therefore a polyolefin that is protected from discoloration or loss of whiteness. The theory is that the discoloration is caused by the combined action of the inhibitor and phenolic antioxidant, and not by either one. However, the inventors do not wish to be bound by this theory. Therefore, the polyolefins of the present invention contain significant amounts of residual catalytic metals, as shown in the first two columns of Table A, that affect discoloration. That is, this type of polyolefin is produced in a manner that leaves a significant amount of residual catalytic metal in the polyolefin, and therefore contains contaminants.
Polyolefins such as those shown in the third column of Table A and those whose residual catalytic metal content is equal to or less than that of the polyolefin are excluded from the scope of the present invention. Furthermore, the polyolefin of the present invention is one that is protected from discoloration without increasing the degree of discoloration when oven aged with the addition of the agent of the present invention. It was determined that some of the polyolefins used in the tests described below additionally contained small proportions of other phenolic antioxidants that were added during the manufacture of the polyolefins immediately after manufacture. One phenolic antioxidant is trademarked Irganox 1076
Octadecyl-β-(3,5-di-t-butyl-4-
It was hydroxyphenyl) propionate. In addition, the polyolefin can contain very small proportions of agents for preventing, adhesion, and antistatic properties. It was found that the addition of a discoloration inhibitor did not impair the antioxidant effects of various phenolic antioxidants. That is, according to the results of oxidative decomposition in an oven test at 150°C, the addition of additives does not promote molecular decomposition. The present invention will now be described by way of examples, the compositions and methods used in these examples being illustrative of what is presently considered best to the inventors. Examples 1 and 2 0.02 g of Ethanox 330 antioxidant and 0.02 g of pentaerythritol were dissolved in 20 g of reagent grade acetone. Exon LPX-2LLDPE was added to this solution and blended. Acetone was removed on a rotary evaporator. Thereafter, the stabilized LLDPE was compression molded in a Pasadena hydraulic press at 300 mm and several
A plaque measuring cm x 10 cm was obtained. Several other 0.15 cm plaques were made in the same manner except that a BASF Wyandotte polyol designated PEP-450 Polyol (P) was used. Yellowness Index (YI) measurements were performed using a Hunter Colorimeter D25D2.
This colorimeter is an instrument that uses light to measure the yellowness of a test polyolef implant against a standard value. Negative and zero values are considered to be very good plastic products and acceptable from an aesthetic point of view. If it shows a positive value greater than about 5, it should be judged that the performance of many products that require whiteness, transparency, etc. is poor. 70℃ in air circulation aging test oven
and aged at both 90℃ and before and after aging.
YI was measured. Tables 1 and 2 contain anti-tarnishing agent, antioxidant-protected
A comparison of YI between LLDPE and a similarly prepared plaque without anti-tarnish agent is shown. [Table] [Table]

Claims (1)

[Scope of Claims] 1. In a polyolefin composition containing a large proportion of polyolefin containing residual catalytic metal impurities that can cause discoloration in the presence of a phenolic antioxidant, and a small proportion of a phenolic antioxidant. , in the composition (a) structure: (wherein R and R' are H or alkyl,
(b) a polyol reaction product obtained from the reaction of propylene oxide with a hydroxyl number of about 500 and pentaerythritol. The composition comprises a compound selected from the group in an amount effective to inhibit and/or prevent discoloration of an antioxidant-protected metal-contaminated polyolefin. 2 The antioxidant is 1,3,5-trimethyl-
2,4,6-tris(3',5'-di-t-butyl-
4'-hydroxybenzyl)benzene, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate and tetrakis[methylene-3-(3',5'-di-t-butyl-4'-) 2. The composition of claim 1, wherein the composition is selected from the group consisting of hydroxyphenyl)propionate]methane. 3. Claim 1, characterized in that said effective amount of said polyol or compound of structure consists of 0.005 to 0.1% by weight of said polyolefin.
Composition of. 4 100 parts by weight of linear low-density polyethylene containing residual catalytic metal impurities in an amount capable of promoting discoloration, 1.
3,5-trimethyl-2,4,6-tris (3',
Composition according to claim 1, characterized in that it contains from 0.05 to 0.2 parts by weight of 5'di-tert-butyl-4'-hydroxybenzyl)benzene and from 0.005 to 0.1 parts by weight of a polyol or a compound of the structure defined above. . 5 About 1.0 parts by weight of a phenolic antioxidant and a polyol reaction product or structure of propylene oxide and pentaerythritol having a hydroxyl value of about 500: (wherein R and R' are H or alkyl,
x is greater than 0 and y is from 0 to 2). 6. A method for producing a polyolefin that prevents and/or suppresses discoloration of a catalytic metal-contaminated polyolefin protected by a phenolic antioxidant, including the polyolefin and an amount effective to suppress and/or prevent discoloration. (a) Structure of: (wherein R and R' are H or alkyl,
(b) a polyol reaction product of propylene oxide and pentaerythritol having a hydroxyl number of about 500; The method characterized in above. 7 0.005 to 0.2 per 100 parts of the polyolefin
7. Process according to claim 6, characterized in that parts of said polyhydroxy hydrocarbon or said reaction product are mixed. 8. The method according to claim 6, characterized in that 1 to 100 parts by weight of the polyhydroxy hydrocarbon or the reaction product are mixed per 100 parts of the phenolic antioxidant contained in the polyolefin. 9 The antioxidant that protects the polyolefin is 1,3,5-trimethyl-2,4,6-tris(3',5'di-t-butyl-4'-hydroxybenzyl)benzene, tris(3,5 -di-t-butyl-4-hydroxybenzyl)isocyanurate and tetrakis[methylene-3-(3',5'-di-t
-butyl-4'-hydroxyphenyl)propionate]methane.