KR100210413B1 - Nylon containing nucleation additives - Google Patents

Abstract

The method of manufacturing a molded article by melting the polymer and forming the molten polymer into a product comprises adding at least about 5 ppm of an additive compound selected from the group consisting of magnesium, calcium and zinc salts of aliphatic dicarboxylic acids having 2 to 14 carbon atoms to the polymer. Is improved.

Description

[Name of invention]

Nylon with nucleation additive

[Background of invention]

The present invention relates to nylon polymers useful in the manufacture of molded articles such as fibers and injection molded articles, and more particularly to nylons containing nucleation additives.

A common problem in melt spinning of highly crystalline nylon homopolymers, such as poly (hexamethylene imiphamide), is the spherulite formation in the polymer of the resulting fibers. Globules are spherical crystals of radial crystals that appear in polymers, typically formed due to inorganic impurities associated with decomposition. When a large number of large spheres are formed, they degrade strength or form defects in the fiber, either of which can result in the cutting of the fiber during spinning or end-use processing. In-room tablets often cause defects or poor uniformity in the final product made from the yarn, which adversely affects product properties for the desired end use. Nylon carpet yarns containing other polymers, such as pigments or polyolefins, which do not mix with nylon, are particularly prone to problems with spherical properties.

Copolymer nylon is less easy to crystallize than homopolymer nylon and consequently, spherical crystal formation is not easy. However, some of these yarns have a reduced level of fiber final pick-up, which results in instability of the filaments during the spinning process, as the frictional forces that the yarns on the process equipment undergo vary. This reduces the uniformity of the yarn, i.e. lowers the dyeing uniformity of the fabric made from the yarn.

In the production of molded articles by injection molding, one speed control step of the process is the time that the mold is closed until the polyamide is sufficiently solidified and removed from the mold without damage. Therefore, it is desirable to have polyamides that crystallize and solidify rapidly while preserving polymer transparency for applications where polymer transparency is desired.

Formulations are known for addition to nylon polymers to affect the nucleation of polyamides, ie for processes where crystallization occurs in molten polymers. For example, as disclosed in US Pat. Nos. 3,755,221, 3,529,929 and 4,176,227, CaF ₂ particles may be added in molten nylon polymer or formed in situ to improve injection molding cycle time or Higher spinning temperatures and higher extrusion speeds are available for melt spinning of nylon fibers. However, such particulates are often inefficient when using CaF ₂ , and fluoride ions in the reactants used in the production of CaF ₂ or fluoride ions in the molten polymer cause corrosion of the processing equipment. CaF ₂ particles also allow the molded article or fibers to have a cloudy appearance that is unsuitable for some end use.

As also disclosed in US Pat. No. 4,919,874, calcium acetate was added to the nylon 6,6 / nylon 6 copolymer to reduce sphericity while maintaining transparency in the fibers. However, the presence of calcium acetate in the polymer significantly reduces the relative viscosity (RV) of the nylon polymer. As a result, calcium acetate as a nucleating agent is generally undesirable and completely unsuitable for some processes requiring high relative viscosity nylon polymers.

[Overview of invention]

It has been found that the addition of certain water soluble additive compounds to nylon polymers provides significant advantages for melt spinning and injection molding processes. Accordingly, the present invention provides a nylon polymer composition and a method for producing a molded article from the composition by melting the polymer and forming the molten polymer into a molded article. The water soluble additive compound used in the composition is selected from the group consisting of magnesium, calcium, zinc salts of aliphatic dicarboxylic acids having 2 to 14 carbon atoms and mixtures thereof. The compound is added in an amount sufficient to provide at least about 5 ppm of the compound in the polymer based on the weight of magnesium, calcium and zinc. According to the compositions and methods of the invention, the nylon polymer is also almost free of fluorides. The present invention is preferably used for polyadipamide polymers.

[Brief Description of Drawings]

FIG. 1 is a graph showing differential scanning calorimetry (DSC) traces of heat flow over time for a conventional nylon 6,6 polymer composition of item 1 of Example 4, showing the crystallization exotherm.

FIG. 2 is a graph as in FIG. 1 for the nylon 6,6 composition containing calcium adipate according to the present invention of the third item of Example 4. FIG.

FIG. 3 shows a nylon copolymer composition in which the curve C contains the calcium adipate according to the invention of item 5 of Example 4 [95 mol% poly (hexamethylene adipamide) and 5 mol% poly (2-methylene Pentamethylene adipamide)]; Curve D is for a similar composition that does not contain the additive of item 4 of Example 4; Curve B is for a similar composition containing calcium hydroxide of item 9 of Example 4; Curve A is the same graph as FIG. 1, with the nylon 66 composition of FIG.

4 is a cross-sectional photomicrograph using 250 times the polarization of nylon 6,6 fibers prepared by allowing the extruded polymer to freely fall from its spinneret under its own weight, i.e. under conditions that promote growth of the spherical well. .

FIG. 5 is a cross-sectional micrograph of nylon 6,6 fibers prepared as described in FIG. 4 except that it contains 20 ppm magnesium adipate (based on the weight of magnesium),

FIG. 6 shows 95 mol% poly (hexamethylene adipamide) and 5 mol% poly, prepared as described in FIG. 4, except that it contains 30 ppm magnesium adipate (based on the weight of magnesium). It is a cross-sectional photomicrograph of a yarn of (2-methylpentamethylene adipamide).

Detailed description of the invention

The nylon polymers used in the present application relate to polyamide homopolymers and copolymers in which aliphatic predominance, ie, less than 85% of the amide bonds of the polymers are attached to two aromatic rings. Widely used nylon polymers and copolymers thereof, such as poly (hexamethylene adipamide) [nylon 66] and poly (e-caproamide) [nylon 6], can be used according to the invention. Other nylon polymers that may be usefully used are nylon 12, nylon 6, 10 and nylon 6, 12.

Polyadipamide in the present application means a nylon polymer wherein at least about 60 mole percent of the amide units of the polyamide are formed from adiphamide units, namely adipic acid. It will be understood that since adipic acid is a divalent acid, basically an equimolar amount of diamine should be present in the polymer, but the term adiamide units refers to amide units formed from adipic acid together with lactams such as caprolactam as well as diamines. Include. Other amide forming species are also possible but are usually very small. For example, triamines such as 4-aminomethyl-1,8-diaminooctane, which acts as a chain brancher, may be mixed in very low amounts.

Preferred homopolymer polyadipamides are hexamethylene adipamide (66 nylon) and tetramethylene adipamide (46 nylon). Homopolymer poly (hexamethylene adipamide) (66 nylon) is particularly preferred for carrying out the present invention.

Preferred polyadipamide copolymers are those comprising at least about 60 mole percent hexamethylene adipamide units. The present invention is particularly useful for preferred polyamides containing at least about 0.2 mole% of 2-methylpentamethylene adipamide units. In addition, other diamine / adipic acid copolymers containing at least about 60 mole percent hexamethylene adipamide units include 2-ethyltetramethylene adipamide units, pentamethylene adipamide units, trimethylhexamethylene adipamide units, and It may contain 1,4-cyclohexyl adipamide units. Copolyamides according to the invention contain hexamethylene terephthalamide units, hexamethylene isophthalamide units, hexamethylene 5-sulfo-isophthalamide units, hexamethylene dodecanediamide units and ε-caproamide units in small amounts can do.

Nylon polymers preferably have a relative viscosity (RV) of about 35 to about 100 when used in fiber production. The relative viscosity when applied to injection molding is typically within the same range as above but may be lower or higher depending on the desired end use characteristics.

The additive compound is a magnesium, calcium or zinc salt of aliphatic dicarboxylic acid having 2 to 14 carbon atoms and may be a mixture of these compounds. Additive compounds include, for example, magnesium, calcium and zinc adipate, glutarate, succinate or oxalate. Magnesium, calcium and zinc adipate are particularly effective and preferred additive compounds for nucleation. The most preferred compound is magnesium adipate because it is very effective when used in small amounts.

Additives are formed in situ by addition of the salt to the polymer itself or by use of suitable reactants. The term added or added is intended in this application to include both the salt itself to the polymer or in situ formation of the compound in the polymer. When the nylon polymer is prepared by polymerization of a polyamide monomer from an aqueous solution, it is preferable to incorporate the additive into the aqueous solution by adding an additive to the aqueous solution because the additive assists in the complete distribution of the compound in the polymer. Preferably, the additive compound is added to the aqueous solution as a salt. However, another suitable method of adding magnesium, calcium or zinc adipate to the polyadipamide polymer is to provide a stoichiometric excess of adipic acid for an amount of diamine equal to a predetermined amount of magnesium, calcium or zinc adipate. Suitable compounds such as Ca (OH) ₂ , CaCO ₃ , Mg (OH) ₂ , MgCO ₃ , Zn (OH) ₂ or ZnCO ₃ , which are sources of magnesium, calcium or zinc ions, can then be added to provide the additive. .

Preferably, it is also possible to add the salt directly to add the compound to the fully formed polymer, but to form it in situ. In either case, suitable measurements should be made to ensure proper mixing in the polymer.

Masterbatches containing low molecular weight carrier polymers and high concentrations of additives can be mixed and melted with the main polymer source to practice the present invention. Similarly, if suitable mixing conditions are used followed by a suitable dehydration and polymer drying step, an aqueous solution of the additive can be used as the vehicle for mixing the additive in the polymer being melted.

The amount of the additive compound is at least about 5 ppm based on the weight of the metal ions of the compound. Preferably, the compound is present in the range of about 5 to about 1000 ppm by weight, most preferably 10 to about 150 ppm. When magnesium, calcium or zinc adipate is used, the typical amount for many fiber spinning processes is 15 to 100 ppm. The lower limit of this range, which is the most preferred range for magnesium adipate, is typically satisfactory because of the high effect of magnesium adipate. Intermediate to redemption values in this range are typically used for calcium and zinc adipates.

The nylon polymers used according to the invention are almost free of fluorides. Almost no fluoride means that the polymer contains a sufficiently low amount of fluoride so that the fluoride does not react with calcium, magnesium or zinc in the polymer to form particles. Since the solubility of calcium, magnesium and zinc fluorides varies, the absence of fluorides substantially depends on the cations present. However, preferably the fluoride ion content is less than 3 parts per million (ppm). Although the polymer may comprise other types of particulate additives such as delusterants, pigments and the like, polymers having few compounds which form particulates by reaction with additive compounds are useful in the process according to the invention. Otherwise, the effect of the additive compound may be reduced.

In the process according to the invention, polymers which are substantially free of monocarboxylic acids and salts thereof are preferred. It is observed that monocarboxylic acids and salts thereof in nylon polymers can significantly reduce the relative viscosity of the polymer. Thus, almost no monocarboxylic acid and salts thereof means that the amount of monocarboxylic acid and salts thereof is low enough to not affect the relative viscosity. Preferably, the amount of monocarboxylic acid or salt thereof is less than about 0.1 mole percent.

The nylon polymer may also contain any known additives for mixing into the polymer, including catalysts, quenchers, antioxidants, pigments and the like, unless the additives adversely affect the process.

The present invention is useful in a variety of known processes for forming molded articles from nylon polymers, including melt spinning, film extrusion, and injection molding processes. The present invention can be usefully used in coupled spin-drawing processes which produce as-spun yarn at low speed and then draw or otherwise process in one or more successive draw steps. Typical of such processes are tow for fully yarn and staple fabrics, and woven nylon spinning processes for producing bulk continuous filament (BCF) yarn for use as carpet yarn. Industrial seals for use on tire cords or air bags are also manufactured using this type of method. The invention is also useful for high speed spinning processes that produce spinning chambers with high orientation due to stress induced crystallization, which may or may not be stretched depending on the desired end use. Typical of this process is a woven nylon spinning process for making yarns partially oriented for use as draw-fabric suppliers or for making fully drawn yarns for important dye end uses.

In the fibers of homopolymer nylons such as homopolymer poly (hexamethylene adipamide) the present invention provides increased levels of crystallization over known spinning processes. The polymers of the cut fibers have an almost invisible sphere with a small sphere size, thus making the structure more uniform to improve the final impregnation rate and dyeing uniformity. This can be seen by comparing the micrographs of FIGS. 5 (invention) and 4 (control). For copolymers such as poly (hexamethylene adipamide) containing at least about 0.2 mol% 2-methylpentamethylene adipamide units, the crystallization rate is increased so that the copolymer can be spun in a manner very similar to homopolymer nylon. And thus the throughput of raw material upon spinning can be increased. This can be seen by comparing curve D (control) and curve A (control polymer nylon 6,6 control) and curve C (invention) in FIG. The final impregnation rate problem is also reduced or eliminated.

When used as a molding resin, the present invention also reduces cycle time while maintaining transparency in the nylon composition.

In the case of regenerated nylon that contains a possible contaminant that changes over time and causes difficulties in the polymer composition and / or end use, the present invention provides a technique that results in a more uniform crystal structure.

The advantages of the present invention can be achieved while avoiding the problems associated with fluoride while maintaining clarity in the polymer without loss of relative viscosity.

[Test Methods]

The relative viscosity of the polyamide was 25 in a solution of 8.4 wt% of the polyamide polymer in a solvent of formic acid containing 10 wt% of water. It is expressed as the ratio of the solution and solvent viscosity measured at.

Tenacity and elongation at break are measured as described by Li in column 2, lines 61 to 3, column 6 of US Pat. No. 4,521,484. The number of measurements used for the sigma calculation is indicated by n = in the table below.

Boil-off shrinkage is measured according to the method of US Pat. No. 3,772,872, column 3, row 49 to column 3,66. The coefficient of variation of the boy-off shrinkage is calculated by using the measure indicated by n =.

CI Acid Blue 122 One-end fabric uniformity is described in the Large Molecule Acid Dye Uniformity Method described in US Pat. No. 5,219,503, column 19, line 34 to column 20, line 18. Is measured using the same process as

Crystallization kinetics of nylon polymers can be measured using differential scanning calorimetry (DSC). The isothermal crystallization test performed by DSC provides basic data for determining the crystallization rate, which can measure the half-life (T _1/2 ) of crystallization. Polymer sample is 20 280 at heating rate per minute Heated in a DSC cell (Perkin-Elmer). Polymer sample was 280 for 3 minutes In molten state at 50 240 with cooling rate of / min Cools down. Polymer sample is 240 It is kept under isothermal conditions for 15 minutes at and the crystallization exotherm is measured. The time at which crystals begin to grow uniformly is seen as the onset of crystallization. The time difference between the exothermic peak and the onset of crystallization is the half life of the crystallization.

The amount of the processing agent was determined by tetrachloroethylene stripping of the processing agent from the actual sample of unit length according to the industry standard test method MATM2706.80 It is measured by measuring the amount of processing agent by infrared absorption in the). Processing agent sigma or processing agent variation coefficient is measured using the number of samples represented by n =.

Example 1

As shown in Table 1, the flakes of homopolymer nylon 6,6 flakes and copolymers incorporating 5 mol% of 2-methylpentamethylene adiamide (Me5-6) were described in US Pat. No. 5,194,620. Was prepared in an autoclave. The RV of the polymer flakes is approximately 47. TiO ₂ was incorporated into the polymer in the amounts indicated. Control was done with two polymers where no nucleation additive compound was used. The present invention is an illustration of using calcium and magnesium adipate as compared to a control without nucleating agent. Calcium and magnesium adipate were added as a salt to an aqueous solution of polyamide monomer before polymerization started in the autoclave.

Using the polymer flakes prepared above, the present invention provides a spin-stretch using a coupled spin-stretch process to produce fully stretched trilobal 60 denier (66 dtex), 20 filament bright yarns. It illustrates by a process. The polymer flakes were extruded in a twin screw extruder and the relative viscosity of the polymer was increased to about 50 before spinning. The extruded filaments were quenched, converged and treated with a spin finish and the resulting yarn was pulled out of the quench zone at a speed of about 1660 mpm. Two low-temperature stretching steps were used to impart approximately 1.9-fold total stretching to the yarn and then heat stabilize to prevent and inhibit shrinkage on the package. The yarn was wound up at a speed of 3485 mpm.

The spinning process used is 30 dynes / w as measured by either the Wilhelmy plate or the DuNuoy ring method. It is a diluent emulsion of a stearate based processing agent containing both hydrophilic and hydrophobic emulsifiers having a surface tension of.

Table 1 shows the measured amount of processing agent, the sigma of the processing agent, toughness sigma, elongation at break, sigma, and coefficient of variation of the boyle-off shrinkage and seed. children. The values for Acid Blue 122 fabric uniformity are shown.

Compared to the first item (control), the second item (invention) is an improved single seed provided by adding 100 ppm of calcium adipate to homopolymer nylon 6,6 containing 0.27% TiO. children. Acid Blue 122 exhibits fabric uniformity. Note the smaller coefficients of processing sigma, toughness sigma and void-off shrinkage.

The third item (invention) compared to the fourth item (control) is a single seed that is equally improved due to the addition of 100 ppm of calcium adipate in homopolymer nylon 6,6 containing 0.02% TiO. children. Acid Blue 122 fabric uniformity is also shown. Note the smaller coefficients of processing sigma and boyle-off shrinkage for the third item of the invention compared to the fourth item for control.

Items 5-9 illustrate the advantages of the present invention in the case of 95/9 mol% nylon 66 / Me5-6 copolymers without or with TiO as the matting agent. With no matting agent in item 5 (invention), low processing agent sigma and improved single acid blue 122 fabric uniformity can be obtained when compared to item 8 (control) with as little as 25 ppm calcium adipate. Compared to the seventh item (control), the sixth item (invention) relates to the addition of calcium adipate with 0.02% matting agent from filaments produced from 95/5 mol% nylon 66 / Me5-6. Indicates. Note that the sigma, coefficient of variation for boy-off shrinkage is significantly reduced and acid blue 122 fabric dye uniformity is improved once.

The ninth item (present invention) illustrates the use of 15 ppm magnesium adipate. Compared to item 8 (control), this lowers the coefficients of variation of the processing agent impregnation rate sigma, toughness sigma, and boy-off shrinkage and increases acid blue 122 fabric uniformity. When comparing item 9 and item 5 (calcium adipate), item 9 containing magnesium adipate has the lowest processing sigma, low toughness sigma, lowest elongation sigma, lowest shrinkage coefficient of variation, best seed. children. Acid Blue 122 provides fabric uniformity and the most stable filament spinning process.

Example 2

The method of Example 1 is repeated using 114 ppm calcium acetate in 95/5 mol% nylon 6,6 / Me5-6 copolymer instead of the nucleating agent according to the present invention. A significant decrease in relative viscosity is observed during the polymerization in the autoclave. In other words, the relative viscosity of the control flakes without calcium acetate is about 50, while the relative viscosity of 40 is obtained for the polymer flakes containing calcium acetate. When attempting polymer spinning using the method of Example 1, the spinning filament is too soft and difficult to control in a quench tube and continuous spinning is not possible.

Example 3

The method of Example 1 is used except that 40 denier (44 dtex), 13 trilobal filament yarn is produced in this series. Table 2 shows the values for the polymer type, amount of TiO used, measured agent variation coefficient, toughness, toughness sigma, elongation, elongation sigma, modulus of 1% and coefficient of variation of boy-off shrinkage.

Example 4

Differential Scanning Calorimetry (DSC) measured for a series of polymer samples as shown in Table 3. Items 1-6 are obtained according to Example 1 above and contain an amount of TiO that changes as indicated. Control items 7 to 9, containing magnesium hydroxide, magnesium oxide and calcium hydroxide, were prepared by mixing the compounds as dry powder in the molten polymer.

Initiation of crystallization and half-life (T) are shown in Table 3.

1 is a DSC trace of the heat flow plotted against the time of the first item (control). 2 is a similar DSC trace for the third item (present invention). In Figure 3, curve C is the DSC trace for item 5 (invention), curve D is for the fourth item (control), curve B is trace for item 9 (control), Curve A is the same as in FIG. 1 for the first item (control).

Example 5

Zinc and magnesium adipate were added to the nylon 6,6 molding compound composition containing 0.2% matting agent as summarized in Table 4 below. The increased crystallinity provided by the present invention has been shown to improve the surface properties (functions and tastes) of articles made with the compositions according to the invention as compared to the control. Molded test rods of these compositions were prepared and the elongation (instron) and shrinkage properties were measured. Table 4 below summarizes the measured properties.

The stresses at maximum load in items 1 and 2 are significantly improved when compared to the control. Surprisingly, unlike the control, test rods of zinc or magnesium adipate did not break when obtained.

Example 6

Differential scanning calorimetry (DSC) measured for homopolymer nylon 6 and nylon 12 with and without magnesium adipate as shown in Table 5. Nylon 6 and Nylon 12 are pure polymers without additives and were used as obtained from Aldrich Chemical Company, Milwauee, Wisconsin 53233. Nylon 6 sample is 20 224 at DSC heating rate per minute Melting point of Nylon 12 samples were 180 at the same DSC measurement conditions. Melting point of In each case, these melting points indicate suitability for use as a molding resin or for melt spinning of fibers. The results are summarized in Table 5 below.

Claims (20)

A method of forming a molded article from a nylon polymer, comprising melting the polymer and forming the molten polymer into a product, the magnesium, calcium of aliphatic dicarboxylic acid having from 2 to 14 carbon atoms in the polymer in the forming tablet. And a water-soluble additive compound selected from the group consisting of zinc salts and mixtures thereof, wherein the compound is at least about 5 ppm in the nylon polymer based on the weight of the magnesium, calcium and zinc when the nylon polymer comprises a homopolymer. And in an amount sufficient to provide from about 5 ppm to about 150 ppm of said compound in said nylon polymer based on the weight of said magnesium, calcium and zinc when said nylon polymer comprises a copolymer, said nylon Characterized by little polymer fluoride How. The method of claim 1, wherein the polymer comprises a polyadipamide polymer. The method of claim 2, wherein the polymer comprises homopolymer poly (hexamethylene adiamide). 3. The method of claim 2, wherein said nylon polymer is a copolymer comprising at least about 60 mole percent hexamethylene adipamide units. The method of claim 4, wherein the copolymer comprises at least about 0.2 mole percent 2-methylpentamethylene adipamide units. The method of claim 1 wherein said nylon polymer is prepared by polymerization of monomers from an aqueous solution and said additive is added to said aqueous solution. The method of claim 1, wherein the method is a melt spinning process for producing nylon fibers, and wherein the water soluble additive compound is applied before melt spinning of the fibers. The method of claim 1 wherein said additive is selected from the group consisting of calcium, magnesium and zinc salts of adipic acid. The method of claim 1 wherein said additive is added to said polymer at about 5 to about 1000 ppm by weight of magnesium, calcium and zinc when said nylon polymer comprises a homopolymer. The method of claim 1 wherein said polymer contains less than about 3 ppm fluoride. The method of claim 1 wherein said polymer is substantially free of monocarboxylic acids and salts thereof. When the nylon polymer comprises a homopolymer, when the nylon polymer comprises a homopolymer, selected from the group consisting of magnesium, calcium and zinc salts of aliphatic dicarboxylic acids having 2 to 14 carbon atoms and mixtures thereof A polymer composition comprising a nearly fluoride-free nylon polymer containing a water-soluble additive compound present at about 5 ppm to about 150 ppm based on the weight of magnesium, calcium and zinc. 13. The composition of claim 12, wherein said polymer comprises a polyadipamide polymer. The composition of claim 13, wherein the polymer comprises homopolymer poly (hexamethylene adipamide). The composition of claim 13, wherein said nylon polymer is a copolymer comprising at least about 60 mole percent hexamethylene adipamide units. The composition of claim 15 wherein said copolymer comprises at least about 0.2 mole percent 2-methylpentamethylene adipamide units. The composition of claim 12 wherein said additive is selected from the group consisting of calcium, magnesium and zinc salts of adipic acid. The composition of claim 12 wherein the additive is added to the polymer at about 5 to about 1000 ppm by weight of magnesium, calcium, and zinc when the nylon polymer comprises a homopolymer. 13. The composition of claim 12, wherein said polymer contains less than about 3 ppm fluoride. 13. The composition of claim 12, wherein said polymer is substantially free of monocarboxylic acids and salts thereof.