CN-121986131-A - Method for subsequent reduction of the free bisphenol A content in polycarbonate and/or polyester carbonate moulding compositions

Abstract

The invention relates to a method for reducing the free BPA content in a molding compound comprising the steps of a) providing a molding compound comprising a) at least one polycarbonate and/or polyester carbonate each comprising structural units derived from bisphenol A, wherein the molding compound is free of vinyl polymers and olefin polymers each functionalized with OH-reactive groups, and wherein the molding compound comprises as component C at least one inorganic filler and/or at least one basic organic colorant according to component D, or wherein the polycarbonate and/or polyester carbonate according to component A is a recycled material, B) melting the molding compound and thoroughly mixing with a polymer B selected from vinyl polymers and olefin polymers each functionalized with OH-reactive groups at a temperature of 200 ℃ to 350 ℃, C) solidifying the melt by cooling, wherein the free bisphenol A content in the molding compound is at least 20ppm at the beginning of the method step a), and molded articles comprising the molding compound obtainable by the method.

Inventors

• D. Wandena
• U. Braschke

Assignees

• 科思创德国股份有限公司

Dates

Publication Date

20260505

Application Date

20241031

Priority Date

20231107

Claims (15)

1. 1. A process for reducing the content of free BPA in molding compounds, Which comprises the following steps: a) Providing a molding compound comprising A) At least one polycarbonate and/or polyester carbonate each containing structural units derived from bisphenol A, Wherein the molding compound is free of vinyl polymers and olefin polymers each functionalized with OH-reactive groups And wherein the molding compound Comprising as component C at least one inorganic filler and/or according to component D at least one basic organic colorant, Or (b) Wherein the polycarbonates and/or polyester carbonates according to component A are recycled materials, B) The molding compound is melted and thoroughly mixed at a temperature of 200 ℃ to 350 ℃ with a polymer B selected from the group consisting of vinyl polymers and olefin polymers each functionalized with OH-reactive groups, C) The melt is solidified by cooling down and, Wherein at the beginning of process step a) the content of free bisphenol A in the molding compound is at least 20ppm.
2. 2. The process of claim 1, wherein component A is a polycarbonate based entirely on bisphenol A.
3. 3. The process as claimed in claim 1 or 2, wherein from 0.2 to 10 parts by weight of component B, based on 100 parts by weight of molding compound, are employed in step a).
4. 4. The process of any of the preceding claims, wherein component B has an average molecular weight Mw of at least 3000 g/mol as measured by gel permeation chromatography at room temperature on polystyrene standards.
5. 5. The process according to any of the preceding claims, wherein the polymer B used in step a) contains OH-reactive groups selected from carboxylic anhydride groups and epoxy groups.
6. 6. The process according to any of the preceding claims, wherein the molding compound comprises as component C at least one inorganic filler and/or according to component D at least one basic organic colorant.
7. 7. A process as claimed in any one of the preceding claims wherein the free bisphenol a content of the moulding compound is from 20 to 2000ppm.
8. 8. The process of any one of the preceding claims, wherein step a) is carried out in the presence of a catalyst.
9. 9. The process of claim 8 wherein the catalyst is selected from the group consisting of phosphorus compounds, antimony compounds, transition metal compounds, nitrogen compounds, and sulfur compounds and mixtures thereof.
10. 10. The process as claimed in any of the preceding claims 8 or 9, wherein 0.0005 to 0.07 parts by weight of catalyst based on 100 parts by weight of molding compound is used in step a).
11. 11. A process according to any one of the preceding claims, wherein step a) is carried out in the presence of a stabilizer, preferably triisooctyl phosphate.
12. 12. The process of any one of the preceding claims, wherein the process is carried out in a process equipment selected from the group consisting of twin screw extruders, planetary roll extruders, internal kneaders and film extruders.
13. 13. The process of any one of the preceding claims, wherein the residence time in step a) is from 10 seconds to 5 minutes.
14. 14. Moulding compounds obtainable by the process according to any of the preceding claims.
15. 15. Molded article comprising a molding compound obtained by the method of any one of claims 1 to 13.

Description

Method for subsequent reduction of the free bisphenol A content in polycarbonate and/or polyester carbonate moulding compositions The invention relates to a method for reducing free bisphenol A in polycarbonate and/or polyester carbonate molding compounds, to the molding compounds obtained by this method and to molded parts comprising such molding compounds. Molding compounds containing polycarbonates and/or polyester carbonates have been used for many years in numerous applications such as in automobile manufacturing, electronics and construction industries. "molding compound" refers to a polymer resin that is produced, for example, by melt compounding (melt processing) polycarbonate with polymer blend partners and/or other components such as fillers, reinforcing agents, colorants, and stabilizers. Molding compounds are generally marketed in the form of pellets and are processed to molded articles, for example by injection molding. By selecting the type and amount of the ingredients, the overall performance profile can be varied over a wide range to meet the respective application requirements. Bisphenol A (BPA) has been the most widely processed monomer unit in polycarbonates for many years. However, the european union is working on reducing BPA release to the environment. This relates to molding compounds (polymer pellets) containing polycarbonate and to semifinished products (i.e. molded parts) and finished products containing polycarbonate. The recommended limit of chemically unbound bisphenol A (free bisphenol A) in molding compounds and semifinished products is in the range from 10 to 150ppm as a prerequisite for future marketing. In the present invention, the proportion expressed in ppm is understood to be the weight proportion (mg/kg). In addition to reducing the content of free BPA in the polycarbonate, its migration scenario can be studied instead, but this requires a significant amount of research expenditure. Optimizing the composition in a stable manner by molding compounds having a reduced free BPA content is known in the art. For example, WO 2018/122138 A1 relates to a composition for producing thermoplastic molding compounds, wherein the composition comprises or consists of a) 30 to 90 wt.% of at least one polymer selected from the group consisting of aromatic polycarbonates, aromatic polyester carbonates and aromatic polyesters, B) 5 to 65 wt.% of a rubber-modified vinyl (co) polymer prepared in a bulk polymerization process which is free of epoxide groups, C) 0.5 to 10 wt.% of a block or graft polymer comprising structural units derived from styrene and at least one epoxide group-containing vinyl monomer, D) 0 to 20 wt.% of one or more further additives, wherein the weight ratio s of structural units derived from styrene to structural units derived from epoxide group-containing vinyl monomers in component C is 100:1 to 1:1. The composition has a low content of free bisphenol A. However, in melt compounding and/or thermoforming to produce molded articles, such as by injection molding processes, degradation of the polymer chains can result in the formation of free bisphenol A in the molding compound and molded article. In melt compounding, the polycarbonate melts and mixes with the other ingredients described above in the melt. Studies have shown that certain ingredients, such as inorganic fillers or inorganic pigments, particularly promote the degradation of the polymer chains and release BPA. However, since these components originally impart advantageous properties to the molding materials, avoiding the use of these components or replacing them with other components is undesirable in most cases. Molding compounds that do not contain components critical to polymer chain degradation may also have high levels of free bisphenol, for example when recycled materials are involved. The recycled material is obtained, for example, by mechanically pulverizing molded articles and reprocessing the pulverized material into pellets by melting. This is the case for post-consumer recycled materials. Likewise, materials that do not reach the desired specifications immediately after the production process can also be remelted. Such materials are known as post-industrial recycled materials. In the present invention, both post-consumer recycled material and post-industrial recycled material are collectively referred to as recycled material. Not only is such a material thermally stressed during its life cycle when melt compounded to produce the original molding compound and subsequently shaped, but the recycling process is also a further step in which thermally induced BPA release may occur. EP 0531008 A1 discloses the production of recycled compositions in which plastic waste made from a composition containing at least one polycarbonate, at least one polyester and at least one impact modifier is melted with an epoxy-functional copolymer derived from at least one unsaturated epoxy compound and at least one ole