RU2174526C1 - Polymeric composite material - Google Patents

Abstract

FIELD: manufacture of transparent polypropylene base composite materials, more particularly manufacture of containers, packing materials disposable glassware and products for constructional purposes. SUBSTANCE: polymeric composite material comprises isostatic polypropylene and/or copolymers thereof and cross-linking agent having mixture consisting of dibenzylidene sorbitol compounds in amount of 0.05-0.5 wt.pts, sterilely hindered phenol in amount of 0.01-0.1 wt.pts and sterilely hindered phosphite in amount of 0.04-0.4 wt. pts per 100 wt.pts of polymer. Invention makes it possible to prepare materials having improved optical characteristics, e.g. light transmission coefficient varies from 38 to 52.6 %, have more dense structure and have high crystallization rate. EFFECT: improved properties of the polymeric composite material. 4 cl, 2 ex, 4 tbl

Description

 The invention relates to the field of production of transparent composite materials based on polypropylene, capable of being processed by injection and / or extrusion method used for the manufacture of containers, packaging materials, disposable tableware, as well as structural products.

To understand the approach to increasing the transparency of crystallizable polymers, we briefly consider the theoretical foundations of crystallization. The polymers crystallize from the melt under the following conditions:
- the molecular structure of the polymer must allow crystallization; insufficient mobility of the main chain, irregular arrangement of side groups, branches or massive side chains can prevent crystallization;
- the crystallization temperature should be below the melting point, but close to the glass transition temperature so that the molecular chains have the necessary mobility for crystallization;
- crystallization requires nuclei, from which crystallites are formed, which are then organized into larger formations;
- the crystallization rate should be significantly high.

It is known that polymers with an average crystallite growth rate, to which PP belongs, to achieve the maximum degree of crystallinity (0.63) need the introduction of artificial nucleating agents (structure-forming agents, nucleators, or nucleating agents). Incomplete crystallization in the manufacture of products leads to the effect of post-crystallization, which is accompanied by warping and cracking of the finished product during operation. The introduction of a structurant should increase the degree of crystallinity of the polymers and accelerate the crystallization rate. In addition, with a homogeneous distribution of the additive in the polymer melt during cooling, a finer-grained and uniform spherulitic structure should be formed. Theoretically, in the formation of the above structure, the PP should be characterized by improved optical properties (increased transparency, reduced turbidity). At the same time, an increase in this degree of crystallinity should be accompanied by an increase in physical and mechanical properties, such as hardness, elastic modulus, tensile strength, etc. However, if finely dispersed talc (melting point> 1000 ^° C) or sodium benzoate (melting point) is used as a structural agent > 300 ^o ), increased transparency of the PP cannot be achieved, on the contrary, the turbidity increases.

For builders based on organic substances, the following requirements can be formulated to achieve maximum efficiency:
- the additive must be wetted or absorbed by the polymer;
- the additive must be insoluble in the polymer;
- the melting point of the additive should be higher than that of the polymer;
- the additive should be distributed homogeneously in the polymer melt.

 Known compositions based on PP or CPL propylene with another α-olefin [JP, application 11-130922, C 08 L 23/10, 1999], characterized by a reduced degree of crystallinity, increased transparency, improved formability of the products and resistant to impact. The effect is achieved by introducing an organic nucleating agent of 1,3,2,4-di (p-methylbenzylidene) sorbitol in an amount of 0.01-1.0 parts by weight and / or 1-1000 ppm of a polymer nucleating agent.

 In the technical solution [US patent 5,856,385, NKI 524/108, 1999] a mixture of dibenzylidene sorbite or its derivatives with amidofunctional compounds is considered as structure-forming agents for PE and PP. With the introduction of these compounds, an increase in transparency is achieved. It is believed that during processing (extrusion, casting), sorbitol destruction is possible due to hydrolysis reactions and, as a result, the negative effect of its conversion products on the quality of polymers. Amidofunctional compounds are introduced to increase the thermal stability of sorbitol derivatives. The ratio of sorbitol / amidofunctional compound 99 / 1-1 / 99 by weight. Recommended dosage is 3 / 1-1 / 3%. It is indicated that the proposed structure-forming mixture can be used together with fillers, heat stabilizers (phosphites, phenols, etc.), light stabilizers, pigments, etc.

 Japanese Patent [JP, Application 64-00140, C 08 L 23/16, 1989] discloses the manufacture by extrusion of sheet and film material from PP or crystallized CPL ethylene with propylene. To achieve increased transparency, reduce turbidity and facilitate formability, a mixture is used consisting of PP (or CPF e / p), 0.01-0.5% monopalmitin and 0.01-0.5% monolaurin as a lubricant, 0.03-0.5% dibenzylidene sorbite or its derivatives as the builder. Films and sheets are recommended for packaging materials.

In the technical solution [US patent 4,954,291, NKI 252 / 315.1, 1990], a mixture of sorbitol of various structures is used with a strict ratio of components maintained in accordance with the formula Z = a / (a + b + c) = 0.3-0.8, where a is dibenzylidene sorbitol or xylitol containing two or three methyl substituents in one aromatic nucleus,
b - dibenzylidene sorbitol or xylitol,
c - dibenzylidene sorbitol or xylitol containing two or three methyl substituents in one aromatic nucleus.

 They achieve an increase in transparency, gloss, bending strength and an increase in the glass transition temperature.

 In the patent [US patent 5,001,176, NKI 524/48, 1991] describes the use of a mixture of dibenzylidene sorbite in an amount of 0.01-1.0% and cyclodextrin in an amount of 0.01-1.0% as a structurant of polyolefins, such as CPL of ethylene with propylene or hexene, butene, PE , PP and others. On the example of CPF of ethylene with propylene or ethylene with propylene and butene-1, an increase in transparency and a decrease in the turbidity of the composition are shown.

 In all of the above technical solutions, an increase in transparency, according to the authors, is achieved due to a decrease in the degree of crystallinity. In all patents considered, the main evaluation criteria were optical characteristics - light transmission and turbidity. In this case, the conclusion of most authors about a decrease in the degree of crystallinity in their compositions is natural, since A well-known fact is that amorphous polymers are characterized by greater transparency.

 At high processing temperatures, a partial change in the structure of sorbitol due to the occurrence of hydrolytic processes is not ruled out, which does not allow achieving the optimum result in terms of transparency and turbidity. Known composition [JP, application 62-235344, C 08 L 23/16, 1987] based on PP and an additive system consisting of A) 0.005-8.0 parts by weight of dibenzylidene sorbite derivatives, B) 0.01-4.0 parts by weight of sterically hindered phosphite; and C) 0.01-4.0 parts by weight of sterically hindered amine (HALS). The additive system according to Japanese patent 62-235344 differs from the ones declared by us and provides the main property of the composition - resistance to increased radiation, i.e. areas of use of materials - various.

The closest in technical essence are the technical solutions described in the patent of the Russian Federation [RU, patent 2128198 C1, C 08 L 23/02, 1999], where the authors consider "mixtures of crystallizable polyolefin, namely polypropylene, with a clarifier powder, which is used as a clarifier derivatives of sorbitol or a mixture of acetal sorbite and xylitol. " The idea is to make a mixture of PP and structure former at temperatures up to 200 ^o , i.e. actually “slightly higher” than the melting point of the PP. In order to prevent agglomeration of the particles of the builder and to improve their distribution in the PP melt (in the case of uneven distribution of the builder in the products, white spots appear), the additives are pre-crushed to the appropriate particle size: average diameter not more than 15 microns. It is believed that if larger particles are used (the maximum particle size of known industrially produced sorbits is 176-420 microns), then processing should be carried out at higher temperatures, above the melting point of sorbitol. However, even subject to the specified temperature conditions, the possibility of agglomeration is not excluded.

The objective of the present invention is to develop a polymeric material based on PP, characterized by a denser structure and improved optical characteristics. The problem is achieved by introducing into the polypropylene structure-forming agent, consisting of a mixture of compounds
- dibenzylidene sorbite (DBL) in an amount of 0.05-0.5 parts by weight;
- sterically hindered phenol (SF) in an amount of 0.01-0.1 parts by weight;
- sterically hindered phosphite (NWP) in an amount of 0.04-0.4 parts by weight;
- per 100 parts by weight of polypropylene (PP).

 In addition, the composite material may contain other known additives, such as fillers, plasticizers, dyes, pigments. The essence of the invention is the use of a new structural agent, consisting of a mixture of components, characterized by their qualitative and quantitative composition.

 The builder can be introduced both in the form of a powdery mixture of the starting components, and in the form of a pre-prepared 10-20% concentrate on PP.

 As the base polymer, practically any industrially produced PP or its copolymers with a melt index from 1.0 to 50.0 g / 10 min, containing or not containing traditional well-known additives of thermal stabilizers from the class of phenols and / or phosphites, plasticizers or lubricants and other technological targets, can be used additives.

где R, R' - H, CH₃, Alk, Ar, -O-Alk, -O-Ar, или их смеси в виде порошков с размером частиц 176-420 мкм.As dibenzylidene sorbitol, compounds of the general formula can be used:

where R, R 'is H, CH ₃ , Alk, Ar, —O — Alk, —O — Ar, or mixtures thereof in the form of powders with a particle size of 176-420 microns.

в виде порошков или гранул (т.н. FF-форма, "легко текучая форма", выпускаемая некоторыми фирмами-производителями добавок для исключения налипания добавок на дозаторах).As SF, sterically hindered phenols of the general formula can be used:

in the form of powders or granules (the so-called FF-form, "easy-flowing form", produced by some manufacturers of additives to prevent the sticking of additives on the dispensers).

As the SPF can be used compounds of General formula
P (OR) ₃ or diphosphites X [P (OR) ₃ ] ₂ , where X is alkyl, aryl and their derivatives, R is alkyl, aryl and their derivatives in the form of powders or granules (the so-called FF form, " easy-flowing form ", manufactured by some manufacturers of additives to prevent the sticking of additives on the dispensers).

When developing the proposed materials used industrially produced compounds. So, for example, as DBS - products of the company Ciba lrgaclear D, lrgaclear DM;
as SF - products of the company Ciba lrganox 1076, lrganox1010;
as SZF - products of the company Ciba lrgafosl68, lrgafosl26.

 The use of other DBS, SF and NWF is also possible.

 The structure-forming mixture can be introduced into polypropylene either at the compounding stage, or at the stage of extrusion molding of a sheet or products, or during molding of products.

The method of preparation of the concentrate
To obtain a 10 - 20% concentrate, a mixture of DBS / SF / SZF is metered into the PP melt through a small additive dispenser during extrusion. You can pre-mix the additives DBS / SF / NWF with granules PP, and then extrude.

Extrusion is carried out at temperature conditions in the zones 210-240 ^o .

 The invention is illustrated by the following examples, in no way limiting the essence of the proposed technical solution.

The introduction of the builder at the stage of compounding PP
PP after synthesis in the form of a powder enters the compounding stage. A mixture of DBS / FS / NWF in the form of a powder or a pre-made 10-20% concentrate on PP is metered through a dispenser of small additives separately or mixed with a stabilizer system lrganox B215 (mixture lrganox 1010 / lrgafos 168 = 1/2). Extrusion is carried out at a temperature in the zones 220-260 ^o . Granulate is obtained from which products are then made.

 Example 1

 (Composition of the prototype).

 Example 2

 For 100 parts by weight PP brand Lipol A7 (JSC Linos, Ukraine) with PTR = 11.9 g / 10 min, containing the traditional stabilizer system 0.05 wt.h. lrganox 1010 and 0.1 wt. h. lrgafos 168 enter the builder mixture lrgaclearD 0.175 parts by weight + lrganox 1010 0.035 parts by weight + lrgafos 168 0.14 parts by weight

 Extrusion is carried out according to the above modes.

The properties are shown in table 4. 1
The composition of the formulations according to examples 3-7 are shown in table 1, parts by weight

 To assess the optical and physico-mechanical properties, standard samples are made by injection molding.

Temperature casting 220-260 ^o
The temperature of the mold 80 ^o .

Physical and mechanical tests are carried out according to the following standards:
Tensile strength - according to GOST 11262
Charpy impact strength - according to GOST 4647.

 Light transmission is evaluated at a wavelength of 425 nm.

The crystallization temperature and thermal effect during melting (ΔH _PL ), which indirectly characterizes the degree of crystallinity, are valued by the DSC method.

 The density of the structure of the molded samples was evaluated by the method of mercury porosimetry according to the indicator "Specific pore volume. This method allows you to evaluate the structure of the sample, quantitatively determine the "density-solidity" of the polymer material. The decrease in porosity, compaction of the structure leads to a decrease in the permeability of gases and other condensing compounds, such as water vapor, volatile solvents. The use of materials with such properties in the manufacture of vacuum packaging, for example, food products or parts-products that are not resistant to oxidation, is quite effective.

 The properties obtained at various dosages of the builder additives are given in table 4.

The introduction of a mixture of additives builders at the stage of injection molding of products from PP
PP granules are pre-mixed, “dusted” with pre-mixed additives DBS / SF / SZF or mixed with a pre-made 10-20% concentrate of additives on PP. The resulting mixture is placed in the hopper of an injection machine for manufacturing products. When pre-mixing the additives with the polymer, one should bear in mind the irreversible losses due to the adherence of the additives on the mixing equipment and the hopper of the injection machine. Therefore, when introducing a structurant at the stage of casting, it is more efficient to use a concentrate.

 The composition of the formulations is shown in table 2, used PP brand Lipol A7 (JSC Linos, Ukraine) with MFR = 11.9 g / 10 min, parts by weight

Temperature casting 220-260 ^o
The temperature of the mold 80 ^o .

 The properties obtained at various dosages of the builder are shown in table 4 (formulations 8-11).

 The introduction of the builder at the stage of manufacturing a sheet or film PP.

PP in the form of granules is fed into the polymer dosing zone (the first extruder zone). A mixture of DBS / SF / NWF in the form of a powder or a pre-made 10-20% concentrate on PP is dosed through a dispenser of small additives into the PP melt or together with the polymer (in the case of preliminary mixing of the powder or granules of the concentrate with PP in the mixer). Get a sheet or film. Extrusion is carried out at a temperature in the zones 220-260 ^o .

 The composition of the formulations is shown in table 3. PP brand Lipol A4 (JSC Linos, Ukraine) with MFR = 3.2 g / 10 min, parts by weight

 Standard samples are cut from the finished sheet to assess the physicomechanical properties.

 The obtained properties at various dosages of the builder are shown in table 4 (formulations 12,13).

 The results shown in table 4 show that, in comparison with the prototype, the PP obtained according to the invention is characterized by improved optical characteristics (increase in light transmittance up to 45% against the prototype 16%). The material has a denser structure - a smaller pore size. In addition, the introduction of the specified builder can 30% reduce the working cycle of casting products due to the acceleration of crystallization processes. Composite materials containing the proposed structure-forming agent are characterized by higher physicomechanical characteristics (yield strength under tension and bending, for example, 39 and 33 MPa versus 33 and 27 MPa, respectively, compared to the prototype).

 All offered additives have a hygienic certificate and are approved for contact with food.

 The proposed structure-forming agent DBS / SF / NWF allows you to reduce the known concentration of DBL in the finished product (PP granules, products from PP) by partially replacing the DBL with SF and NWF and, as a result, reduce the cost of the finished product.

Claims (3)

1. A polymer composite material comprising isotactic polypropylene and / or its copolymers and a structure-forming agent, characterized in that it as a structure-forming substance contains a mixture consisting of compounds of dibenzylidene sorbite, sterically hindered phenol and sterically hindered phosphite, in the following ratio of material components, wt. hours:
Polypropylene - 100
Dibenzylidene sorbitol - 0.05 - 0.5
Sterically hindered phenol - 0.1 - 0.1
Sterically hindered phosphite - 0.4 - 0.4
2. The polymer composite material according to claim 1, characterized in that the compounds of the general formula are used as dibenzylidene sorbite

where R, R 'is H, CH ₃ , Alk, -0-Alk, -0-Ar,
or mixtures thereof. 3. The polymer composite material according to claim 1, characterized in that as sterically hindered phenol use compounds of the General formula

or mixtures thereof. 4. The polymer composite material according to claim 1, characterized in that as sterically hindered phosphite use compounds of the general formula P (OR) ₃ or X [P (OR) ₃ ] ₂ , where X and R are alkyl, aryl, or their derivatives, or mixtures thereof.

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