MXPA00011758A - Nucleation of polyamides in the presence of hypophosphite - Google Patents

Abstract

The present invention provides polyamide compositions comprising a polyamide, nylon 2,2, and a phosphorous-containing whitening agent having Formula (I), wherein R is hydrogen, an alkyl group with 1 to 6 carbons, a cycloalkyl group with 5 to 6 carbons, or a phenyl or methylphenyl aromatic group, and M is hydrogen or a metal. In a preferred embodiment, the polyamide is nylon 6,6 (polyhexamethylene adipamide) and the phosphorous-containing whitening agent is a hypophosphorous acid or a metal hypophosphite. Sodium hypophosphite is especially preferred. The polyamide compositions of the present invention have improved molding cycle times, and are tough, white and color-stable.

Description

NUCLEATION OF POLAS IDAS IN THE PRESENCE OF HYPOPHOSPHIT BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to the production of synthetic polyamide compositions having a high degree of whiteness and stability and color and improved time of the molding cycle.

DESCRIPTION OF THE RELATED TECHNIQUE The polymerization of suitable diamines with dicarboxylic oxides to form polyamides is well known in the art and is of considerable commercial importance. Polyamides have a variety of uses. An important commercial use is resin for molding articles, especially items that require strength and the ability to withstand heat. Nucleators have often been used to improve the time of the molding cycle or the crystallization rate of the polyamides. For example, the patent of E.U.A. No. 3,080,345 discloses the use of a nucleating agent sodium phenylphosphonate, sodium isobutylphosphonate, magnesium oxide, mercuric bromide, mercuric chloride, cadmium acetate, lead acetate or phenophthalein. The patents of E.U.A. Nos. 3,585,264 and 4,866,115 also disclose the use of nucleating agents to improve the crystallization rate of polyamides. Hypophosphite compounds have been used as catalysts for the polymerization of polyamides, for example in the patents of E.U.A. Nos. 3,860,558; 3,173,898; and 3,691, 131. In the patents of E.U.A.

Nos. 3,860,558 and 3,691, 131, metal hypophosphites are used together with a clogged phenolic compound as an antioxidant. In the patent of E.U.A. 3,173,898, hypophosphites of certain metals are used in small concentrations. The use of hypophosphites in the polymerization process also gives the polyamide a greater degree of whiteness and color stability. One problem in making polyamides is that most nucleators are made much less effective in the presence of hypophosphite.

Therefore, there is a need for polyamide compositions and manufacturing processes that have the advantages imparted by the use of a nucleator, such as reduced time of the molding cycle, while still allowing the use of hypophosphites.

BRIEF DESCRIPTION OF THE INVENTION One aspect of the present invention is a polyamide composition comprising (a) a polyamide other than nylon 2,2, (b) a phosphorus-containing whitening agent having the formula (I): wherein R is hydrogen, an alkyl group with 1 to 6 carbons, a cycloalkyl group with 5 to 6 carbons, or an aromatic phenyl or methyl phenyl group, and M is hydrogen or a metal, and (c) nylon 2.2 in an amount effective to cause the nucleation of the polyamide different from nylon 2.2. The polyamide of part (a) is preferably nylon 6,6 and the phosphorus-containing whitening agent of part (b) is preferably selected from the group consisting of hypophosphorous acid and metal salts thereof. More preferably, the phosphorus-containing emblissing agent is a metal hypophosphite in which the metal of the la, lia or llb groups of the periodic table is selected. Sodium hypophosphite is especially preferred. In a particular embodiment, the composition contains the phosphorus-containing whitening agent in an amount between about 5 ppm and 500 ppm phosphorus by weight, more preferably between about 20 ppm and 80 ppm phosphorus by weight. Nylon 2.2 is preferably present in an amount between about 2 ppm and 2000 ppm by weight, more preferably between about 5 ppm and 50 ppm by weight. Another aspect of the invention is a process for producing nucleated polyamide, which comprises employing a different nylon 2.2 melted polyamide in the presence of a whitening agent containing phosphorus and nylon 2.2 in an amount effective to cause nucleation of the polyamide. The compositions of the present invention exhibit resistance5, commercially desirable whiteness and color stability, however, also have improved molding cycle times. The polyamide compositions of the invention can be recrystallized at relatively high temperatures without substantial deterioration of the strength of the final product. The higher recrystallization temperatures mean that the material needs less time to cool off from the melt, because it hardens before the temperature drops from the melt. This improves the molding cycle time and increases performance and productivity.

DESCRIPTION OF THE ILLUSTRATIVE MODALITIES 15 The polyamides of the present invention are condensation polymers obtained by the polycondensation of aminocarboxylic acids or mixtures of diamines and dicarboxylic acids including interpolyamides obtained by the polycondensation of different polyamide forming components. Preferred polyamides are the class generally known as nylons. A particularly preferred polyamide is polyhexamethylene adipamide, nylon 6,6. This invention is useful for polyamides in all forms, but is especially useful for the resins of ^^ ^^^^ & ^ ^^^^ ^ ^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^ - L ^ ^ g »^^^^^ * ^^^ * polyamide to be used for molding items. Useful forms of polyamides include combinations, alloys and copolymers thereof. Preferred copolymers are copolymers of nylon 6,6 with nylon 6, nylon 61A, nylon 6TA and the like. The phosphorus-containing whitening agents of the present invention are preferably hypophosphites and more preferably hypophosphorous acid or metal hypophosphites, wherein the metal is preferably from the group la, lia, or llb of the periodic table. For example, the metal can be lithium, sodium, potassium, barium, magnesium, calcium, strontium or zinc. The manganese transition metal can be used. The preferred metal hypophosphite is sodium hypophosphite. The nylon 2.2 and the phosphorus-containing bulking agent can be incorporated into the polyamide before, during or after the polycondensation step. Preferably, the phosphorus-containing whitening agent is added during the polycondensation step to result in a white polymer. The polymerization due to the oxidation of the polycondensation can not be reversed by the subsequent addition of phosphorus-containing whitening agent; however, phosphorus-containing whitening agents show efficacy as color stabilizers in the subsequent melting and melting process of the polymer. Thus, nylon 2.2 and the phosphorus-containing whitening agent can be added to the polymer-forming ingredients before the polycondensation step or during the polycondensation process and the reaction completed by heating. 2.2 nylon can be added to the polyamide already formed by adding it to the molten polyamide. Preferably, 2.2 nylon can be mixed with the solid polyamide. Alternatively, the solid polyamide in the form of lumps, pellets or chips can be coated or sprinkled with the ingredients and then the polyamide can be melted. Preferably, the nylon 2.2 can be incorporated into a set of polyamide pellets, while the phosphorus-containing whitening agent is incorporated into a second set of polyamide pellets. Then the two sets of polyamide pellets are mixed and melted. In another embodiment, a set of polyamide pellets containing nylon 2.2 and the phosphorus-containing whitening agent are mixed and melted with a second set of polyamide pellets containing only the phosphorus-containing whitening agent. The polyamide compositions of the present invention may further comprise polymer additives known to those skilled in the art, including fillers, reinforcing agents, stabilizers, colorants, flame retardants, mold release agents, plasticizers, pigments, coating agents, ultraviolet light absorption, antistatic agents, lubricants and the like, which may be added in effective amounts and which do not detrimentally affect the compositions in the present invention.

^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^; The following examples are included to demonstrate the preferred embodiments of the invention. It should be appreciated by those skilled in the art that the methods set forth in the following examples represent methods discovered by the inventor to function well in the practice of the invention and can thus be considered to be preferred models for their practice. However, those skilled in the art will appreciate, in light of the present disclosure, that various changes may be made in the specific embodiments that are set forth and still obtain an equal or similar result without deviating from the spirit and scope of the invention.

COMPARATIVE EXAMPLE 1 The nylon 6,6 molding resin compositions comprising a phosphorus-containing whitening agent, specifically sodium hypophosphite, were prepared to compare the addition results of talc, a known nucleating agent, with the results when it is not added talcum powder. A conventional nylon 6.6 pellet control composition commercially available from Solutia Inc. under the trade name VYDYNE® was formed. To this control composition is added 70 ppm phosphorus by weight of sodium hypophosphite. The control composition will be referred to in the present composition 1. Two concentrates of basic mixture were formed by sprinkling 5% either of Cimpact 699 or Mistron a *, * Superfrost, both being talc types commercially obtainable from Luzenac, to VYDYNE pellets as described above. Both dragee pellet formulations are then processed on a ZSK-40 double worm extruder at a barrel temperature of 275 ° C. The parts were molded by a combination of processes of the pellets of composition 1 and the pellets of the basic mixture fed into a machine by injection molding. The percentages of the pellets of the basic mixture added to the formulations of the combination of procedures were 0% for a control formulation or 2% for each type of the basic mixture to produce two formulations containing talc, each with a concentration of talc final 0.1%. Tension strength, elongation to failure and recrystallization temperature were measured for the molded parts, formed from the control and the two formulations containing talc, by methods known in the art. The results are given in table 1.

TABLE 1 * * * '' * "* - 'As shown in Table 1, the addition of talc as a nucleating agent raised the recrystallization temperature relative to the control without added nucleating agent, a result which is desirable since it would result in However, the addition of talc to nylon 6,6 in the presence of sodium hypophosphite resulted in a reduction in elongation to failure of more than 50% in relation to the control. Failure is unacceptable for a commercial product that requires significant retention of resistance.

EXAMPLE 2 Nylon 6,6 resin compositions were prepared for molding with sodium hypophosphite added in the presence of nylon 2.2 from 0 ppm to 22 ppm. A master batch was formed by sprinkling 500 ppm of a powder containing 2.2 to about 80 wt.% Nylon, commercially available from L. Bruggemann as P22, on VYDYNE pellets, as described above. The master batch was nylon 2.2 of approximately 440 ppm. The dusted pellets were then combined in a Killion individual worm extruder with a barrel diameter of 3.81 cm, with a length / diameter ratio of 24/1, equipped with a metering pump, and a Maillifer type worm at barrel temperatures of 280 ° C. 285 ° C. Pellets of composition 1 were also provided as described in comparative example 1. The molding was carried out by a method of mixing pellets of composition 1 and pellets of the masterbatch fed in an injection molding machine. The percentages of the master batch pellets added to the formulations of the process mixture ranged from 0% to 5%, resulting in 2.2 nylon concentrations from 0 to 22 ppm. Tensile strength, elongation to failure and recrystallization temperature were measured for five 2.2 nylon formulations between 0 ppm and 22 ppm, by techniques known in the art. For example, recrystallization was measured in a DSC-7 (Perkin-Elmer) at a maximum exotherm level after 1 minute at 50 ° C, heating from 50 ° C to 285 ° C at 20 ° C / min, 5 min. at 285 ° C, and cooling from 285 ° C to 50 ° C at 20 ° C / min. The results are given in table 2.

TABLE 2 In all cases in which nylon 2.2 was added, the recrystallization temperature increased by at least 8.0 ° C. However, unlike the comparative example, the use of nylon 2.2 between 4.4 ppm and 22 ppm in the presence of a phosphorus-containing bleaching agent, specifically sodium hypophosphite, did not lead to an unacceptable decrease in the percentage of elongation to the mistake. For four of the 5 test formulations, the failure elongation percentage was between 83% and 106% of the corresponding value for the control formulation. Also, the tensile strength was not impaired by the use of nylon 2.2 as a nucleating agent in the presence of sodium hypophosphite. All compositions and methods described and claimed in The present can be realized and implemented without undue experimentation in light of the present disclosure. Although the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the art that variations may be applied to the compositions and methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain agents that are chemically related can substitute for the agents described herein, although the same or similar results would be obtained. All substitutes and Similar modifications apparent to those skilled in the art appear to be within the spirit, scope and concept of the invention as defined by the appended claims.

Claims (18)

NOVELTY OF THE INVENTION CLAIMS

1. - A polyamide composition comprising (a) a nylon 2.2 different polyamide, (b) a phosphorus-containing bleaching agent having the formula I: Formula I: H R - P = 0 OM wherein R is hydrogen, an alkyl group with 1 to 6 carbons, a cycloalkyl group with 5 to 6 carbons, or an aromatic phenyl or methylphenyl group, and M is hydrogen or a metal, and (c) nylon 2.2 in a effective amount to cause the nucleation of the polyamide different from nylon 2.2.

2. The composition according to claim 1, further characterized in that the polyamide of (a) is nylon 6,6.

3. The composition according to claim 1, further characterized in that the phosphorus-containing bleaching agent is a metal hypophosphite, and the metal in the metal hypophosphite is selected from the groups la, lia or llb of the periodic table. .

. 4. The composition according to claim 3, further characterized in that the metal hypophosphite is sodium hypophosphite.

5. The composition according to claim 4, further characterized in that the metal hypophosphite is present in an amount between about 5 ppm and 500 ppm phosphorus by weight.

6. The composition according to claim 4, further characterized in that the metal hypophosphite is present in an amount between about 20 ppm and 80 ppm phosphorus by weight.

7. The composition according to claim 1, further characterized in that nylon 2.2 is present in an amount between about 2 ppm and 2000 ppm by weight.

8. The composition according to claim 1, further characterized in that nylon 2.2 is present in an amount between about 5 ppm and 50 ppm by weight.

9. A composition comprising nylon 6,6; a phosphorus-containing bleaching agent having the formula I: Formula I: wherein R is hydrogen, an alkyl group with 1 to 6 carbons, a cycloalkyl group with 5 to 6 carbons, or an aromatic phenyl or methylphenyl group, and M is hydrogen or a metal; and nylon 2,2 in an amount effective to cause the nucleation of nylon 6,6.

10. A process for producing nucleated polyamide, characterized in that it comprises cooling a different nylon 2.2 melted polyamide in the presence of (a) a phosphorus-containing bleaching agent having the formula I: Formula I: wherein R is hydrogen, an alkyl group with 1 to 6 carbons, a cycloalkyl group with 5 to 6 carbons, or an aromatic phenyl or methylphenyl group, and M is hydrogen or a metal; and (b) nylon 2.2 in an amount effective to cause nucleation of the polyamide.

11. The process according to claim 10, further characterized in that the polyamide is nylon 6.6.

12. The process according to claim 10, further characterized in that the phosphorus-containing bleaching agent is a metal hypophosphite, and the metal in the metal hypophosphite is selected from the groups la, lia or llb of the periodic table .

13. The process according to claim 12, further characterized in that the metal hypophosphite is sodium hypophosphite.

14. The process according to claim 13, further characterized in that the metal hypophosphite is present in an amount between about 5 ppm and 500 ppm phosphorus by weight.

15. The process according to claim 13, further characterized in that the metal hypophosphite is present in an amount between about 20 ppm and 80 ppm phosphorus by weight.

16. The process according to claim 10, further characterized in that nylon 2.2 is present in an amount between about 2 ppm and 2000 ppm by weight.

17. The process according to claim 10, further characterized in that the nylon 2.2 is present in an amount between about 5 ppm and 50 ppm by weight.

18. A process for producing nylon 6,6 nucleated, further characterized in that it comprises cooling melted nylon 6,6 in the presence of metal hypophosphite and nylon 2,2 in an amount effective to cause nucleation of nylon 6,6. j. -Í- ¿-... i ttí &MÍáMH ~