Patent Application
20230060016
The invention relates generally to recycled polyethylene terephthalate (PET) compositions, which is a suitable material for producing apparel accessories, such as button, zipper puller, cord lock, cord end, stopper, etc. In the industry of apparel accessories, there is a need to use recycled polyethylene terephthalate to produce apparel accessories to achieve better sustainability market need.
In the apparel accessory industry, recycled polyethylene terephthalate (RPET) is highly desirable for the production of different apparel accessories, such as buttons, zipper pullers, cord locks, cord ends, stoppers, etc. to achieve better sustainability.
However, pure RPET is not suitable for injection molding due to: very long cycle times, mold sticking problems, sink marks, etc. In addition, during injection molding, RPET becomes increasingly yellow, which indicates color instability. The instability of the color in the molded material makes the use of pure RPET to produce apparel accessories in various colors very difficult.
Commercialized PET material that is sold for injection molding seldom contains recycled content. Those commercial grades that contain recycled content usually contain glass fibers/minerals/inorganic fibers. Glass fiber would be exposed on the surface of the molded part, which causes cosmetic defects. Furthermore, it is undesirable to use glass fiber in the industry of apparel accessories because of the potential “dangerous image” to have glass on clothes.
Thus, there is a need to provide a modified recycled PET material without glass or inorganic fibers, and which is suitable for the production of apparel accessories via injection molding.
This object is accomplished according to the invention by a recycled PET product that contains a combination of RPET, virgin PET and other ingredients to create a product that is suitable for injection molding, color-stable, and glass-free.
The composition according to the invention is made of the following components, in combination with the percentages given by weight % of RPET of the entire composition, and phr (parts per hundred resin of RPET) for the other components:
1. Recycled Polyethylene Terephthalate, from any source, including mechanical recycling, chemical recycling, or biochemical recycling. The RPET can be bright or semi-dull, in an amount of >90 wt %.
2. Virgin Polyethylene Terephthalate, in the form of homopolymer or copolymer, with intrinsic viscosity larger than 1.0 dL/g in an amount of 0-7 phr.
3. A nucleation agent selected from salts of citrate acid (anhydrous or dihydrate), or salts of carbonic acid (untreated or treated with stearic acid), titanium oxide and mixtures thereof in an amount to 0.2-1 phr.
4. An impact modifier in the form of an unsaturated organic compound selected from the group consisting of maleic, acrylic, methacrylic, itaconic, crotonic, alpha-methyl crotonic and cinnamic acids, anhydrides, esters and their metal salts. Examples are: EMA-GMA (ethylene-methyl acrylate-glycidyl methacrylate terpolymer), PP-g-MAH (polypropylene grafted maleic anhydride), PE-g-MAH (Polyethylene grafted maleic anhydride), POE-g-MAH (functionalized polyolefin elastomer grafted maleic anhydride), and their mixture, in an amount of 2-4 phr.
5. An optical brightener in the form of a compound having at least four conjugated double bonds, such as —C═C—C═C—C═C—C═C— or —N═C—C═C—C═N—C═C— in its molecule structure. Examples are 2,5-Bis(5-tert-butyl-2-benzoxazolyl)thiophene, 4,4′-Bis(5-methyl-2-benzoxazolyl)stilbene, 2,2′-(1,2-Ethenediyldi-4,1-phenylene)bisbenzoxazole, 1-(2-Cyanostyryl)-4-(4-cyanostyryl)benzene, 4,4-Bis(diethylphosphonomethyl)biphenyl, Disodium 4,4′-bis(2-sulfostyryl)biphenyl, and mixtures thereof, in an amount of 0-1 phr.
6. A heat stabilizer including primary antioxidants or secondary antioxidants in an amount of 0-0.2 phr. The primary antioxidants include hindered phenols and secondary aromatic amines. Examples are: Pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate, octadecyl-3-[3,5-di-tert-butyl hydroxyphenyl]propionate], 3,3′,3′,5,5′,5′-hexa-tert-butyl-a,a′,a′-(mesitylene-2,4,6-triyl)tri-p-cresol, calcium-bis (((3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)methyl)-ethylphosphonate), bis (oxyethylene) bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)-propionate), 3,5-bis (1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl esters, and mixtures thereof.
The secondary antioxidants include phosphorus compounds. Examples are tris(2,4-ditert-butylphenyl)phosphite, Bis(2,4-di-tert-butylphenyl) Pentaerythritol Diphosphite, Tris(dipropyleneglycol) phosphite, Calcium bis[monoethyl(3,5-di-tert-butyl-4-hydroxylbenzyl)phosphonate], and mixtures thereof.
7. A wax, particularly a polyolefin based wax. Examples are: PE-wax, PP-wax, and mixtures thereof, in an amount of 0-1.5 phr.
The components listed above are mixed, melted and pelletized by extrusion. The pelletized composition is then placed in an injection molding machine to create the desired molded parts. The specific combinations of these components led to a composition that is suitable for use in injection molding, with short cycle times, low degree of sticking, and importantly, no yellowing. Molded parts for apparel can be made using the composition according to the invention, in particular zipper pullers, cord ends, cord locks, buttons or any other molded parts that could be made using PET.
The following will describe specific examples of RPET compositions according to the invention. The Examples are for illustration of various compositions within the scope of the invention and are not intended as a limitation of the claims. The compositions described in the examples are made by mixing the listed components, melting, pelletizing by extrusion and then placing them in an injection molding machine to mold various products that are then tested for strength, shrinkage and color.
In the examples, the following abbreviations are defined as follows:
RPET=Recycled Polyethylene Terephthalate
PET=Virgin Polyethylene Terephthalate
TiO2=Titanium Oxide
NA=Nucleation Agent
IM=Impact modifier
OB=Optical brightener
Pri-HS=Primary Heat Stabilizer
Sec-HS=Secondary Heat Stabilizer
The amounts in each example are given as a percent by weight of RPET of the entire composition, and as PHR (parts per hundred resin) of the other components. The other components are defined as parts per hundred parts of RPET.
RPET: 96.9 wt %
NA(trisodium citrate) 0.2 phr
IM(PE-g-MAH): 2.0 phr
OB: 1.0 phr
(2,2′-(1,2-Ethenediyldi-4,1-phenylene)bisbenzoxazole)
RPET: 96.5 wt %
NA (trisodium citrate): 0.6 phr
IM (EMA-GMA): 2.0 phr
OB: 1.0 phr
(2,2′-(1,2-Ethenediyldi-4,1-phenylene)bisbenzoxazole)
RPET: 91.7 wt %
PET: 5.0 phr
NA (trisodium citrate): 1.0 phr
IM (PP-g-MAH): 2.0 phr
OB: 1.0 phr
(2,2′-(1,2-Ethenediyldi-4,1-phenylene)bisbenzoxazole)
RPET: 90.1 wt %
PET: 5.0 phr
NA(trisodium citrate): 1.0 phr
IM (PP-g-MAH): 4.0 phr
OB: 1.0 phr
(2,2′-(1,2-Ethenediyldi-4,1-phenylene)bisbenzoxazole)
RPET: 90.1 wt %
PET: 7.0 phr
NA (trisodium citrate): 1.0 phr
IM (PP-g-MAH): 2.0 phr
OB: 1.0 phr
(2,2′-(1,2-Ethenediyldi-4,1-phenylene)bisbenzoxazole)
RPET: 90.3 wt %
PET: 7.0 phr
TiO2: 0.3 phr
NA (trisodium citrate): 1.0 phr
IM (PP-g-MAH): 2.0 phr
RPET: 90.2 wt %
PET: 7.0 phr
NA (trisodium citrate): 1.0 phr
IM (PP-g-MAH): 2.0 phr
Pri-HS: 0.2 phr
(Pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate)
Sec-HS: 0.2 phr
(tris(2,4-ditert-butylphenyl)phosphite)
Wax (PE): 0.5 phr
RPET: 90.3 wt %
PET: 7.0 phr
TiO2: 0.3 phr
NA (CaCO3) 1.0 phr
IM (PP-g-MAH): 2.0 phr
Pri-HS: 0.2 phr
(Pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate)
Sec-HS: 0.2 phr
(tris(2,4-ditert-butylphenyl)phosphite)
RPET: 95.1 wt %
TiO2: 0.3 phr
NA (trisodium citrate) 1.0 phr
IM (PP-g-MAH): 2.0 phr
Pri-HS: 0.2 phr
(Pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate)
Sec-HS: 0.2 phr
(tris(2,4-ditert-butylphenyl)phosphite)
Wax (PE-wax) 1.5 phr
The compositions are set forth in the table 1 below:
Each of the compositions was tested for tensile strength, shrinkage in the mold, and color. The results are listed in Table 2 below:
As can be seen from Table 2, the products produced according to the invention exhibit no serious shrinkage, evidenced by sink marks, little yellowing, and high tensile strength, especially when compared to a reference sample of pure RPET, which is yellowish, exhibits serious shrinkage and has a significantly lower tensile strength as compared to the compositions according to the invention.
The compositions according to the invention have many advantages, especially when compared to pure RPET or virgin PET.
The present invention has the advantage of being made with >90% Recycled content, and greater than 95% content of polyethylene terephthalate. The compositions are highly suitable for injection molding, yielding a cycle time within 20 seconds. The compositions of the present invention exhibit low shrinkage and improving sink marks when comparing to 100% recycled PET.
In addition, the compositions of the present invention make RPET processable by injection molding without requiring the addition of glass, minerals or inorganic fibers, yet is still able to be colored to commercial standards.
Furthermore, the compositions according to the invention have increased tensile strength of between 2 and 14 times that of 100% recycled PET as well as increased color stability when compared to 100% recycled PET. The composition according to the present invention avoids the use of any polymers that do not consist of hydrogen, oxygen, and carbon.
