ES2709724T3 - Bioresin-based peroxide masterbatch - Google Patents

Abstract

Stock mixture comprising one or more organic peroxides in liquid form, dispersed in a polymer matrix comprising at least 50% by weight of a bioresin containing 14C, wherein the polymer matrix has a porosity, expressed as a percentage of pores in the volume of the matrix and determined by mercury absorption according to the description, from 2.5-5 70% by volume and the concentration of water in the mother liquor as determined by Karl Fischer coulombimetric titration as the description is maintained at 2,000 ppm or less, depending on the total weight of the mother mix.

Description

DESCRIPTION

Bioresin-based peroxide masterbatch

The present application relates to a masterbatch comprising one or more organic peroxides dispersed in a bioresin. It also relates to a process for the preparation of this masterbatch and to the use of this masterbatch for the modification of polymers.

The masterbatches are concentrates of additives, in this case organic peroxides, which can be used in the processing of polymers, particularly olefin polymers. The masterbatches can be used to add organic peroxides to the polymer to be processed in order to improve the dispersion of the peroxide in said polymer and improve the ease of dosing, especially when the user is unable to handle the organic peroxides in liquid form. .

The masterbatches are generally obtained by dispersing high concentrations of the peroxides in materials that are compatible with the polymer to be processed. In order to obtain the best profitability of use, the concentrates must contain usable quantities up to, and including, the greatest possible amount of peroxide, at the same time that they allow to achieve an efficient dispersion of the peroxide when said master mixtures are diluted in the polymer that is going to process.

In view of the growing market for bio-resins and the increasing number of bioresin applications, it is desirable to provide a masterbatch containing a peroxide dispersed in a bioresin. In addition, it is desired to provide a masterbatch which, when used to modify a bioresin, does not lead to an unacceptable hydrolysis of said bioresin. This is important because several bio-resins, for example, polylactic acid (PLA), are highly susceptible to hydrolysis during processing.

For example, the residual moisture content of PLA before injection molding should not exceed 100 ppm and before extrusion should not exceed 250 ppm. Because the PLA is very hygroscopic, which leads to the absorption of a multiple of this amount in a few hours, the PLA must be dried immediately before processing or packaged in an appropriate manner so that moisture absorption is not possible. Obviously, the subsequent addition of a masterbatch that leads to a significant increase in water content is not desirable. Therefore, it is important that the masterbatch contain a relatively low water content.

Accordingly, the invention relates to a masterbatch comprising one or more organic peroxides in liquid form, dispersed in a polymer matrix comprising at least 50% by weight of a bioresin, wherein the polymer matrix has a porosity, expressed as a percentage of pores in the volume of the matrix, of 2.5-70% by volume and the concentration of water in the masterbatch is maintained at 2,000 ppm or less, according to the total weight of the masterbatch.

The peroxide or peroxides are present in the masterbatch in liquid form. This means that the peroxides must be liquid at room temperature or must be dissolved in a solvent that can evaporate from the product.

Peroxides with a half-life of 1 hour of at least 77 ° C, measured in a 0.1 M monochlorobenzene solution using DSC-TAM are preferred.

Examples of said peroxides include (3,5,5-trimethylhexanoyl) peroxide, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, 1,1,3,3- peroxy-2-ethylhexanoate tetramethylbutyl, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy-diethylacetate, t-butyl peroxy-isobutyrate, 1,1-di (tert-butylperoxy) -3 , 3,5-trimethylcyclohexane, 1,1-di (t-amylperoxy) cyclohexane, 1,1-di (t-butylperoxy) cyclohexane, tamilo peroxy-2-ethylhexyl carbonate, t-amyl peroxyacetate, t-butyl acetate -butyl, t-butyl peroxy-3,5,5-trimethylhexanoate, 2,2-di (t-butylperoxy) butane, t-butyl peroxy-isopropyl carbonate, t-butyl peroxy-2-ethylhexyl carbonate, peroxybenzoate tamilo, t-butyl peroxybenzoate, 4,4-di (t-butylperoxy) butyl valerate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butyl cumylperoxide, dicumyl peroxide, di (t-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, di (t-butyl) peroxide, di (t-amyl) peroxide, h isopropylcumyl idroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 3,3,5,7,7-pentamethyl-1,2,4-trioxepane, cumyl hydroperoxide, t-butyl hydroperoxide, t-hydroperoxide amyl and ketone peroxides dimeric and trimeric ketones represented by the formulas I-II.

wherein R1-R6 are independently selected from the group consisting of hydrogen, C ¹ -C ²⁰ alkyl, cycloalkyl C ³ -C ^20, aryl of C ⁶ -C ²⁰ aralkyl and C ⁷ -C ²⁰ alkaryl C ⁷ -C ^20, which groups may include linear or branched alkyl; and each of R ¹ -R ⁶ may be optionally substituted with one or more groups selected from hydroxy, alkoxy, linear or branched alkyl, aryloxy, ester, carboxy, nitrile, and amido.

The most preferred peroxides are di (t-butyl) peroxide, di (t-amyl) peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, tert-butyl-2-ethylhexyl-carbonate. -butyl, tert-amyl peroxy-2-ethylhexyl carbonate, 3,3,5,7,7-pentamethyl-1,2,4-trioxepane and 3,6,9-triethyl-3,6,9-trimethyl -1,4,7-triperoxonan.

The total concentration of peroxide in the polymer matrix is preferably 50% by weight or less, based on the polymer matrix, more preferably 3-45% by weight, and most preferably 4-40% by weight. The polymer matrix comprises at least 50% by weight of a bioresin. The term "bioresin" in this description refers to the polymer that originates from renewable materials, ie materials, for example, of animal or vegetable origin, whose stocks can be replaced in a short time at a human scale . It is necessary, in particular, that these stocks can be renewed as quickly as they are consumed. Unlike materials derived from fossil sources, renewable materials contain 14C.

All carbon samples extracted from living organisms (animals or plants) are in fact a mixture of 3 isotopes: 12C (representing approximately 98.892%), 13C (approximately 1.108%) and 14C (traces: 1.2 ^ 10 " 10% The 14C / 12C ratio of living tissue is identical to that of the atmosphere.In a living organism, the 14C / 12C ratio is kept constant by the metabolism, since the carbon is continuously exchanged with the external environment. mean of 14C / 12C is equal to 1.2 ^ 10-12%.

E L12C is stable, that is, the number of atoms of 12C in a given sample is constant over time. 14C is radioactive and the number of 14C atoms in a sample decreases over time with a half-life of 5,730 years. Consequently, the presence of 14C in a material, in any quantity, indicates that the atoms of C that form that molecule come from renewable raw materials and not from ancient sources of hydrocarbons.

Therefore, a "bioresin" according to this specification contains 14C.

The 14C / 12C ratio in a material can be determined by one of the methods described in ASTM D6866-05 (Standard Test Methods for Determining the Biobased Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis, March 2005 ), preferably Method B described therein.

Examples of bio-resins are polyolefins such as polyethylene, polypropylene, ethylene polymer and vinyl acetate, and mixtures thereof prepared from renewable resources. A preferred polyolefin is polypropylene. The term "polypropylene" refers to polymers that comprise at least 50 mol% of polypropylene units.

A preferred class of bio-resins are biopolymers, that is, polymers that are produced in, or are produced by, a living organism or are produced from monomers or oligomers derived from plants and / or animals.

Examples of such polymers are polylactic acid (PLA), polyhydroxyalkanoates (PHA), such as polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxybutyrate-cohydroxyvalerate (PHBV), and polyhydroxybutyrate -co-hydroxyhexanoate (PHBV), and polybutylene succinates (PBS) such as polybutylene succinates (PBS), and polybutylene succinate-co-adipate (PBSA).

The bioresin can be of a polymerization reactor quality or an extruded porous quality. The porosity of the polymer matrix, expressed as percentage of pores, is from 2.5 to 70% by volume, more preferably from 5 to 65% by volume, and more preferably from 10 to 60% by volume. This porosity is determined by the absorption of mercury according to ISO 15901-1 (2005). Said matrices are commercially available. If the porosity is too high, the peroxide can be extracted from the pores.

The concentration of water in the masterbatch is maintained at less than or equal to 2,000 ppm, preferably at less than 1,500 ppm and most preferably at less than 1,000 ppm, based on the total weight of the masterbatch. Water has a negative influence on various types of polymers and, therefore, the water content must be kept low. For example, when the masterbatches are used in biopolymers, such as polylactic acid, the water will cause the hydrolysis of the biopolymer during further processing, which is obviously undesirable.

Therefore, it is desired to dry the polymer matrix before incorporation of the peroxide to achieve a water content below the limit mentioned above. Therefore, the resulting masterbatch should also be packaged so that the water content does not exceed 2,000 ppm of water during a storage period of at least 6 months. The water content is determined using the coulometric Karl Fischer titration as described in the examples.

The masterbatch according to the present invention can be prepared by impregnation of the polymeric matrix with a liquid peroxide or a peroxide formulation. Said formulation may contain the peroxide in a solvent, in a total concentration of 10-60% by weight, more preferably 20-55% by weight, and most preferably 30-50% by weight.

Suitable solvents include linear and branched hydrocarbon solvents, such as isododecane, tetradecane, tridecane, Isopar® M, Exxsol® D80, Exxsol® D100, Exxsol® D100S, Soltrol® 145, Soltrol® 170, Varsol® 80, Varsol® 110, Shellsol® D100, Shellsol® D70, Halpasol® i 235/265, and mixtures thereof. Particularly preferred phlegmatizers are Isopar® M and Soltrol® 170.

Preferably, the solvent has a boiling point of 95% in the range of 200-260 ° C, more preferably 225-255 ° C, most preferably 235-250 ° C. The boiling point of 95% is the boiling point (bp) to which 95% by weight of the solvent is evaporated, or in the case of a single solvent compound, such as tetradecane, the boiling point of this compound. Normally, 95% of the boiling point is obtained from conventional analytical methods such as ASTM-D5399.

The impregnation can be done by contacting the liquid peroxide or the liquid peroxide-containing formulation with the polymer matrix.

In order to reduce the risk of dust explosions and introduction of water into the system, the impregnation is preferably carried out under an inert atmosphere (eg, nitrogen). The peroxide (formulation) is preferably added slowly to the polymer matrix. After the addition of the peroxide (formulation) to the matrix, the resulting mixture is preferably mixed for, for example, 10-120 minutes, more preferably 20-90 minutes. After that, the solvent can be removed by evaporation, if desired.

After impregnation, and before or after the removal of the solvent, the resulting masterbatch can be aged. This aging can be carried out at any temperature below the SADT (auto-accelerated decomposition temperature) of the peroxide and at any time in the range of 2 hours to several days.

The polymer matrix can be impregnated with a single liquid peroxide, but it can also be impregnated with two or more peroxides.

The masterbatch according to the present invention may optionally contain certain additives as long as these additives do not have a significant negative effect on the safety, transportability and / or storage stability of the formulation. Examples of such additives include: antiozonants, antioxidants, antidegradants, UV stabilizers, coagents, fungicides, antistatic agents, pigments, dyes, coupling agents, dispersing agents, blowing agents, lubricants, processing oils, and mold release agents. These additives can be used in their usual amounts. The present invention also relates to the use of said masterbatches in methods of modifying polymers, such as the modification of polylactic acid to improve its melt strength by long chain branching.

The masterbatch is preferably added to said polymer in an amount of 0.01-1.5% by weight, more preferably 0.05-1.0% by weight, and most preferably 0.08-0.8. % by weight, calculated as peroxide and based on the weight of the polymer. The masterbatch according to the present invention is also suitable for compatibilizing mixtures of biopolymers.

Examples

Example 1

Polylactic acid (PLA) with a porosity of 65% and a water content of 3,000 ppm was dried for 5 days in a climate box at a temperature of 50 ° C and a relative humidity of 10%. The water content of the PLA after this drying procedure was analyzed to be 1,000 ppm, which was also confirmed by the measured weight loss of 2,000 ppm.

This water content was analyzed as follows. A sample of approximately 300 mg is weighed in a 5 ml vial and capped with a septum. The vial was heated at 120 ° C for 5 min in a Metrohm 832 Thermoprep. The headspace of the gas was purged with dry nitrogen in a Karl Fischer solution (Hydranal Coulomat AG). The water content was determined by coulometric measurement with a Metrohm 831 KF coulombometer. A blank determination was made using a sample vial for reference.

The porosity of the PLA was determined by the intrusion of mercury according to ISO 15901-1: Evaluation of pore size distribution and porosimetry of solid materials by mercury porosimetry and gas adsorption - Part 1: Mercury porosimetry. The instrument used was a Micromeritics Autopore 9505 porosimeter in the pressure range from ford to 220 MPa. Prior to the measurement, the PLA was dried at 35 ° C for 6 hours.

A Nauta mixer was purged with dry air to maintain the conditions without humidity and was charged with the dried porous PLA. Subsequently, trimeric methyl ethyl ketone methyl peroxide (17% by weight based on the total masterbatch) was added dropwise as a 41% by weight solution in isoparaffins (Trigonox® 301). After mixing for 1-2 hours, the slightly moistened material was transferred to a double aluminum bag (inner sealed by tape, outer seal). The material was left to mature for 5 days. This resulted in a masterbatch product with dry appearance and a water content of 500 ppm.

Example 2

Example 1 was repeated, except that Trigonox®101 (2,5-dimethyl-2,5-di (t-butylperoxy) hexane was used as peroxide and charged to the PLA at a concentration of 39% by weight.

The resulting masterbatch had a water content less than 1000 ppm.

Example 3

Polylactic acid (PLA) with a porosity of 65% and a water content of 3,000 ppm was dried by adding it to a Nauta mixer and purging it with a flow of dry air for a certain period of time, with occasional mixing, until it was obtained the water content below 1,000 ppm. The water content of the final dried PLA was 400 ppm.

The Nauta mixer was kept under a flow of dry air and 40% by weight of Trigonox® 17 (t-butylperoxy 2-ethylhexyl carbonate) was added using the same procedure described for the addition of peroxide in Example 1.

The resulting masterbatch had a water content of less than 1,000 ppm.

Example 4

The caking cylinders (synthetic, with two semi-removable walls, 5 cm internal diameter and 7 cm high) were filled with the masterbatches of Examples 1, 2 and 3 (approximately 36 g). The masterbatches were covered with a lid and a load of 0.46 kg was placed on top of each to simulate the pressure conditions as if 25 kg of product were packaged in a bag in a carton with a lower surface of 38 x 28 cm The caking cylinders were stored in a weather chamber for 2 months at 25 ° C / 50% RH. After this period, the fillers and lids were removed and the capping cylinders were carefully opened to visually inspect whether the caking had occurred. The masterbatches of examples 1 and 2 did not show caking, while only a slight caking was observed in the masterbatch of Example 3. With the lower applied force, the latter returned to free flow.

Claims (13)

A masterbatch comprising one or more organic peroxides in liquid form, dispersed in a polymeric matrix comprising at least 50% by weight of a bioresin containing 14C, wherein the polymer matrix has a porosity, expressed as a percentage of pores in the volume of the matrix and determined by mercury absorption according to the description, of 2.5-70% in volume and the concentration of water in the masterbatch as determined by Karl Fischer coulometry titration according to the description is kept at 2,000 ppm or less, depending on the total weight of the masterbatch. 2. Masterbatch according to claim 1, wherein the bioresin is a polymer that is produced in, or is produced by, a living organism or that is produced from monomers or oligomers derived from plants or animals. 3. Masterbatch according to claim 2, wherein the bioresin is polylactic acid. 4. Masterbatch according to any one of the preceding claims, wherein at least one of the one or more organic peroxides is selected from organic peroxides having a half-life of one hour at a temperature of 77 ° C or more. The masterbatch according to claim 4, wherein at least one of the one or more organic peroxides is selected from the group consisting of t-butyl peroxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5. -di (tert-butylperoxy) hexane, and cyclic ketone peroxides having a structure according to one of the following formulas:

wherein R1 -R6 * are independently selected from the group consisting of hydrogen, alkyl of C ¹ -C ^20, cycloalkyl C ³ -C ^20, aryl of C ⁶ -C ²⁰ aralkyl and C ⁷ -C ²⁰ alkaryl C ⁷ -C ²⁰ , whose groups may include linear or branched alkyl moieties; and each of R ¹ -R ⁶ may be optionally substituted with one or more groups selected from hydroxy, alkoxy, linear or branched alkyl, aryloxy, ester, carboxy, nitrile, and amido. 6. Masterbatch according to claim 5, wherein the cyclic ketone peroxide is 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonan. 7. Masterbatch according to any one of the preceding claims, comprising 4-40% by weight of organic peroxide. 8. Masterbatch according to any one of the preceding claims, wherein the polymer matrix has a porosity of 10-65% by volume. 9. Masterbatch according to any one of the preceding claims, further comprising a solvent. 10. Use of a masterbatch according to any one of the preceding claims, for the modification of polymers. 11. Use according to claim 10, for improving the melt strength of the polylactic acid. 12. Process for the preparation of a masterbatch according to any one of claims 1 9, comprising the steps of (i) providing a polymer matrix comprising at least 50% by weight of a bioresin and having a porosity, expressed as a percentage of pores in the volume of the matrix, and determined by mercury absorption according to the description, of 2, 5-70% by volume and a water content as determined by coulometric Karl Fischer titration according to the description, less than or equal to 2,000 ppm, and (ii) impregnating said polymer matrix with one or more peroxides in liquid form. 13. Process according to claim 12, wherein the water content of the bioresin is less than or equal to 1,000 ppm.