RU2238284C2 - Saturated complex polyester for making plastic container with high thermal stability and gas impermeability and method for it preparing - Google Patents

Abstract

FIELD: polymers, chemical technology.

SUBSTANCE: invention relates to saturated complex polyester that is used as a material for molded containers - bottles, caps and so on. Polyester based on aromatic dicarboxylic acid or its derivative and ethylene glycol comprises from 20 ppm to 10% of nano-dimensional particles of silicon dioxide with average diameter 3-100 nm from polyester mass. The latter is prepared by interaction of sodium silicate with water to form sodium hydrosilicate that is passed through column packed with cation-exchange resin to obtain small-dispersed particles of silicon dioxide with average diameter 0.5-1.0 nm and the following growing crystals of particles up to average diameter 3-100 nm. The turbidity index of polyester in its liquid state is 10.9% or less. Invention can enhance thermal stability and gas impermeability of polyester-base containers.

EFFECT: improved preparing method, valuable properties of polyester.

6 cl, 1 tbl, 10 ex

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to saturated polyester, which is widely used as a material for various molded containers, such as plastic bottles, plastic cups, etc., and more particularly to a saturated polyester having high heat resistance and high gas impermeability in the presence of nanosized particles. silicon dioxide in the polymer chain, and to a method for producing a saturated polyester.

Prior art

A saturated polyester such as polyethylene terephthalate ((PET) (PET)) or polybutylene terephthalate ((PBT) (PBT)) is a linear thermoplastic polymer containing ester bonds in the main chain. Since the saturated polyester has excellent dimensional stability, weather resistance and surface smoothness and has high transparency and a glossy appearance, it is widely used as a material for various molded products, such as synthetic fibers, films, containers, cases, etc.

However, the saturated polyester has the disadvantage that since it has a low glass transition temperature (T _g ), poor heat resistance and gas permeability to certain gases, it cannot be used as packaging material for fruit drinks, beer, green tea products, rice drinks etc.

To overcome these drawbacks, polyethylene naphthalate (PEN) resin and a mixed polymer of polyethylene terephthalate and polyethylene naphthalate are proposed. These products are currently in use. However, the cost of polyethylene naphthalate (PEN) resin is high compared to polyethylene terephthalate and, thus, it is economically inefficient. In addition, it is difficult to regenerate polyethylene naphthalate resin. Alternatively, a method for improving heat resistance and gas permeability is discussed in Japanese Patent Laid-open No. 1997-290457. According to the method, the orientation of the polyester crystals is improved by biaxially stretching during the molding of the PET bottle. However, some difficulties in this method are that the degree of orientation of the crystals cannot reach above 40%, and it cannot be used if the drink is poured into a PET bottle at a high temperature above 92 ° C. In addition, in the case of pouring at low temperature, the performance drops.

SUMMARY OF THE INVENTION

Therefore, the present invention is aimed at eliminating the above problems, and the aim of the present invention is to provide a saturated polyester for plastic containers having high heat resistance and high gas impermeability while uniformly dispersing nanosized particles of silicon dioxide in a polyester with an increase in crystal orientation above 40%.

Another objective of the present invention is to provide a method for producing a saturated polyester for plastic containers having high heat resistance and high gas impermeability.

The present invention provides a saturated polyester comprising nanosized particles of silicon dioxide, wherein the nanosized particles of silicon dioxide have an average particle diameter of 3-100 nm and are present in an amount of from 20 ppm to 10 wt.% Based on the weight of the saturated polyester .

The saturated polyester in accordance with the present invention is obtained by introducing nanosized particles of silicon dioxide in the process of transesterification or esterification followed by polycondensation of the starting materials.

Further, the present invention will be explained in more detail.

Typically, a saturated polyester is prepared from aromatic dicarboxylic acid or an ester-forming derivative and ethylene glycol as starting materials. If desired, other starting materials may be added. Examples of aromatic dicarboxylic acid used in the present invention include isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, phthalic acid, adipic acid, sebacic acid, and mixtures thereof. As examples of the glycol used in the present invention, a small amount of propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. may be added to ethylene glycol.

If necessary, the saturated polyester may additionally contain additives such as thermal stabilizers, anti-sticking agents, antioxidants, antistatic agents, UV absorbers, etc.

In accordance with the present invention, nanosized particles of silicon dioxide are introduced in the process of producing a saturated polyester. At this time, nanosized particles of silicon dioxide should maintain a constant size during the reaction.

The nanosized silica particles used in the present invention are prepared as follows: first, sodium silicate (Na ₄ Si) is reacted with water to produce sodium hydrosilicate. Then, sodium hydrosilicate is passed through a cation exchange resin column. Sodium oxide adsorbed by a cation exchange resin is removed to obtain finely divided particles of silicon dioxide. Thus obtained fine particles of silicon dioxide have an average particle diameter of 0.5-1.0 nm. Finally, to obtain nanosized particles of silicon dioxide having the desired size, crystals are grown from nanosized particles of silicon dioxide.

Thus obtained nanosized particles of silicon dioxide show good dispersibility in water. However, since nanosized silica particles rapidly agglomerate when water is lost due to the low boiling point of water, they are stored in a liquid having a high boiling point, such as ethylene glycol or butanediol. In particular, to minimize adverse reactions with the saturated polyester, the silica particles are preferably dispersed in ethylene glycol (EG). Nanosized particles of silicon dioxide having the same average particle diameter can be used individually, or two or more types of nanosized particles of silicon dioxide having a different average particle diameter can be mixed with each other. To obtain a suspension containing nanosized particles of silicon dioxide, the solvent can be used separately, or two or more solvents can be mixed with each other.

The amount of nanosized silica particles added is preferably in the range of 20 ppm to 10 wt.% And more preferably in the range of 50 ppm to 6 wt.%, Based on the weight of saturated polyester. When the number of nanosized particles of silicon dioxide is less than 20 ppm, the physical properties of the saturated polyester according to the present invention are insufficient. When the number of nanosized particles of silicon dioxide exceeds 10 wt.%, Good dispersibility of nanosized particles of silicon dioxide in the polymer is not achieved, and the transparency of the saturated polyester becomes low due to particle agglomeration. In accordance with the present invention, the particles of silicon dioxide have an average particle diameter of 3-100 nm. When the average particle diameter of the silica is more than 100 nm, the transparency becomes poor. When the average particle diameter of the silica is less than 3 nm, dispersibility and transparency are poor due to the surface tension between the particles.

To improve the color tone of the resin, phosphoric compounds, for example trimethyl phosphate (TMP), triethyl phosphate (TEF), triphenyl phosphate (TFP), can be introduced together with nanosized particles of silicon dioxide. Given the equivalent ratio with metal ions, the amount of phosphorus compounds introduced is adjusted to make the phosphorus content in the polymer equal to 0.01-0.1 wt.% With respect to the weight of the polymer.

As described above, in order to improve the dispersibility of nanosized particles of silicon dioxide, it is preferable that the particles are pre-dispersed in water, ethylene glycol, butanediol or mixtures thereof to obtain a suspension. The concentration of nanosized particles of silicon dioxide in the suspension is preferably in the range of 3-30 wt.% And more preferably in the range of 5-20 wt.%, Relative to the weight of the suspension. When the concentration of nanosized particles of silicon dioxide in the suspension is less than 3 wt.%, Too much suspension is introduced, causing adverse reactions as a result. When the concentration of nanosized particles of silicon dioxide in the suspension is above 30 wt.%, The dispersibility of the particles becomes poor and a large number of coarse particles are formed. To improve the dispersibility of particles, smaller particles make the concentration of the suspension less. When the particle size is largest, the concentration of particles in the suspension can be increased.

When introducing a suspension containing a suspension of nanosized particles of silicon dioxide, during the synthesis of the polyester it is noted that nanosized particles of silicon dioxide should not agglomerate with each other. In accordance with the present invention, the molar ratio (E / T) of ethylene glycol (EG) to dimethyl terephthalate (DMT) is preferably in the range 1.8-2.5, and the molar ratio (E / T) of ethylene glycol (EG) to terephthalic acid (TFA) ) is preferably in the range of 1.3-2.5. Ways to improve the dispersibility of nanosized particles of silicon dioxide in the polyester are not specifically limited, but because a suspension of particles in water can cause adverse reactions in the DMT method, the particles are preferably dispersed in ethylene glycol (EG) or butanediol (DB). In the TFA (terephthalic acid) method, despite the fact that the suspension contains water, there are no difficulties in carrying out the reaction. However, the DMT method is superior to the TFA method in terms of particle dispersibility.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is described in more detail below using examples and comparative examples. These examples are provided for illustrative purposes only, and should not be construed as limiting the scope of the invention.

Example 1

100 parts by weight dimethyl terephthalate (DMT) and 64 parts by weight ethylene glycol (EG) is loaded into the reactor and a dispersion of 0.03 parts by weight is added thereto with stirring. antimony trioxide and 0.06 wt.h. manganese acetate tetrahydrate in 3 parts by weight ethylene glycol. The mixture is heated at a temperature of 130-230 ° C and subjected to transesterification for 4 hours to form BHT (BHT) (bis (2-hydroxyethyl) terephthalate) (B-1). A suspension of 10 wt.% Silica particles having an average particle diameter of 50 nm in ethylene glycol is passed through a filter with a mesh size of 0.5 μm to obtain a suspension (S-1). When the temperature of B-1 reaches about 235 ° C., a dilution of 0.03 parts by weight trimethylphosphate (TMF) in 2 parts by weight ethylene glycol is loaded into the reactor and then 20 parts by weight are slowly added. suspensions S-1. BHT is passed through a filter with a cell size of 3 μm. After heating the filtrate for 50 minutes at a temperature of 235-285 ° C, polycondensation is carried out for 3 hours to obtain a polymer (P-1-1) having the physical properties shown in Table 1 below. The polymer is cut into chips. The chopped chips are loaded into a general solid state polymerization reactor to obtain a polymer (P-1-2) having the properties shown in the table below. When using a machine for blowing bottles of heat-resistant PET get 500 cm ³ heat-resistant bottles (P-1-3) from (P-1-2).

Example 2

Polymers and bottles of heat-resistant PET receive the same way as in example 1, except that 1 wt.h. suspensions of nanosized particles of silicon dioxide S-1 are added to the BHT at a temperature of 235 ° C and subjected to polycondensation.

Example 3

Polymers and bottles made of heat-resistant PET are prepared in the same manner as in Example 1, except that silica particles having an average particle diameter of 15 nm are used to prepare an S-1 suspension instead of silica particles having an average particle diameter of 50 nm .

Example 4

Polymers and bottles of heat-resistant PET receive the same way as in example 1, except that 1 wt.h. a suspension of nanosized particles of silicon dioxide S-1 obtained in example 3, is added to the BHT at a temperature of 235 ° C and subjected to polycondensation.

Example 5

100 parts by weight terephthalic acid and 75 parts by weight ethylene glycol is loaded into the reactor. The mixture is heated at a temperature of from 30 ° C to 230 ° C with stirring and subjected to esterification for 6 hours to obtain OSH. Then 175 parts by weight suspensions of EG and TFA (molar ratio: 2.0) are added to BHT within 2 hours, the reaction is additionally carried out for 1.5 hours while maintaining the reaction temperature of 230 ° C. 175 parts by weight BHT is passed through a filter with a mesh size of 3.0 μm and the filtrate is transferred to a polycondensation reactor. 0.02 wt.% Phosphoric acid with respect to the weight of the polymer is introduced into the polycondensation reactor and then a dilution of 0.015 wt.% Of the antimony trioxide is added to the weight of the polymer in a small amount of ethylene glycol. Silica particles having an average particle diameter of 15 nm are dispersed in 10 wt.% Ethylene glycol to give a suspension. The suspension is passed through a filter with a mesh size of 0.5 μm to obtain a suspension of S-2. 20 parts by weight suspensions are added to BHT at a temperature of 230 ° C. After heating the BHT for 50 min at a temperature of 230-285 ° C, polycondensation is carried out for 3 hours to obtain a polymer having the physical properties shown in the table below. The polymer is cut into crumbs (P-5-1). The chopped chips are loaded into a solid-state polymerization reactor and subjected to solid-phase polymerization to obtain a polymer (P-5-2) having the physical properties shown in the table below.

Using a machine for blowing bottles from heat-resistant PET, 500 cm ³ heat-resistant bottles (P-5-3) are obtained from (P-5-2).

Example 6

Polymers and bottles of heat-resistant PET receive the same way as in example 5, except that 1 wt.h. suspensions of nanosized particles of silicon dioxide S-2 are added to the BHT at a temperature of 235 ° C and subjected to polycondensation.

Example 7

Polymers and bottles made of heat-resistant PET are prepared in the same manner as in Example 5, except that silica particles having an average particle diameter of 3 nm are used to prepare an S-2 suspension instead of silica particles having an average particle diameter of 15 nm .

Example 8

Polymers and bottles of heat-resistant PET receive the same way as in example 7, except that 0.05 wt.h. a suspension of nanosized particles of silicon dioxide S-2 obtained in example 7, is added to the BHT at a temperature of 235 ° C and subjected to polycondensation.

Example 9

Polymers and bottles of heat-resistant PET receive the same way as in example 5, except that 50 wt.h. S-2 suspensions containing silica particles having an average particle diameter of 100 nm, are added to the BHT at a temperature of 230 ° C. and polycondensed instead of silica particles having an average particle diameter of 15 nm.

Example 10

Polymers and bottles of heat-resistant PET receive in the same manner as in example 5, except that 0.05 wt.h. a S-2 suspension containing silica particles having an average particle diameter of 100 nm, instead of silica particles having an average particle diameter of 15 nm, polycondensation.

Comparative Example 1

100 parts by weight terephthalic acid and 75 parts by weight ethylene glycol is loaded into the reactor. The mixture is heated at a temperature of 230 ° C. with stirring and subjected to esterification for 6 hours to obtain OSH. After adding 175 parts by weight suspensions of EG and TFA (molar ratio: 2.0) to BHT for 2 hours, the reaction is additionally carried out for 1.5 hours while maintaining the reaction temperature of 230 ° C. 175 parts by weight BHT is passed through a filter with a mesh size of 3.0 μm, and the filtrate is transferred to a polycondensation reactor. 0.02 wt.% Phosphoric acid relative to the weight of the polymer is introduced into the polycondensation reactor, and then a dilution of 0.015 wt.% Antimony trioxide with respect to the weight of the polymer in a small amount of ethylene glycol is added thereto. After heating the BHT for 50 min at a temperature of 230-285 ° C, polycondensation is carried out for 3 hours to obtain a polymer (P-11-1) having the physical properties shown in the table below. The polymer is cut into crumbs (P-5-1). The resulting chips are loaded into a solid-state polymerization reactor and subjected to solid-phase polymerization to obtain a polymer (P-11-2) having the properties shown in the table below. Using a machine for blowing bottles from heat-resistant PET, 500 cm ³ heat-resistant bottles (P-11-3) from (P-11-2) are obtained.

Reference Example 2

Polymers and bottles made of heat-resistant PET are obtained in the same manner as in Example 5, except that silica particles having an average particle diameter of 20 nm are used to prepare an S-2 suspension instead of silica particles having an average particle diameter of 15 nm .

Reference Example 3

Polymers and bottles of heat-resistant PET receive the same manner as in comparative example 2, except that 1 wt.h. Suspensions of S-2 containing silica particles having an average particle diameter of 200 nm are added to the BHT at a temperature of 230 ° C. and subjected to polycondensation instead of silica particles having an average particle diameter of 20 nm.

Reference Example 4

Polymers and bottles of heat-resistant PET are obtained in the same manner as in example 5, except that particles of silicon dioxide having an average particle diameter of 100 nm relative to the weight of the polymer are used at a concentration of 100 ppm to obtain a suspension of S- 2. In this example, since the particles of silicon dioxide in the polymer agglomerate with each other in the form of impurities having a size of about 3 mm, solid phase polymerization is not carried out.

The physical properties of polymers and bottles of heat-resistant PET obtained in the examples and comparative examples are shown in the table.

Heat resistance and gas impermeability to 0 ₂ is determined as follows:

Heat resistance

The temperature resistance of the bottles is expressed as the temperature resistance. First, the water is heated to a certain temperature, which is the initial temperature resistance temperature, and it is instantly poured into the bottle. Then evaluate the stability of the morphology of the bottle.

Gas tight to O ₂

The bottle is protected against oxygen using epoxy. Nitrogen gas is loaded into the bottle at a certain rate and then discharged from the bottle. The concentration of oxygen contained in gaseous nitrogen is determined. Based on the concentration, the amount of oxygen entering the bottle externally in 24 hours is calculated.

As described above, the present invention provides a saturated polyester having excellent heat resistance and high gas impermeability, for example, to O ₂ . Therefore, the saturated polyester product of the present invention is used as material for various bottles containing drinks or food.

Although preferred embodiments of the present invention have been considered for illustrative purposes, those skilled in the art will recognize that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the invention, as discussed in the appended claims.

Claims (6)

1. A saturated polyester for plastic containers based on aromatic dicarboxylic acid or its derivative and ethylene glycol, containing from 20 ppm to 10% by weight of polyester nanosized particles of silicon dioxide with an average diameter of 3-100 nm, obtained by the interaction of sodium silicate with water with the formation of sodium hydrosilicate, which is passed through a column with a cation exchange resin to remove sodium oxide, to obtain fine particles of silicon dioxide with an average diameter of 0.5-1.0 nm, and subsequent growth crystals of fine particles to an average diameter of 3-100 nm, and the polyester in the liquid state has a turbidity of 10.9% or less. 2. The saturated polyester according to claim 1, characterized in that the nanosized particles of silicon dioxide are introduced into the polyester as a dispersion during the esterification of aromatic dicarboxylic acid or transesterification of its derivative with ethylene glycol followed by polycondensation in the liquid phase. 3. The saturated polyester according to claim 1, characterized in that the polyester is polyethylene terephthalate. 4. A method of obtaining a saturated complex polyester for plastic containers, carried out by esterification of aromatic dicarboxylic acid or transesterification of its derivative with ethylene glycol, introducing at this stage a dispersion of silicon dioxide nanoparticles with an average diameter of 3-100 nm in an amount of from 20 ppm to 10% by weight of the polyester followed by liquid polycondensation to form a polyester with a turbidity of 10.9% or less. 5. The method according to claim 4, characterized in that the dispersion of silicon dioxide nanoparticles contains 3-30% silicon dioxide. 6. The method according to PP.4 and 5, characterized in that the solvent for obtaining the dispersion is ethylene glycol.