RO132577B1 - Polymeric composite based on natural rubber and plasticized starch - Google Patents

Description

The invention relates to a polymeric composite based on natural rubber and laminated starch, and to the process for obtaining it. These materials are made on machinery specific to the rubber processing industry, namely: mixer, roller, press, etc. The starch is laminated and then incorporated into the roll or into the mixer in the natural rubber, after which the other components are introduced; the obtained mixture is processed into finished products by vulcanization in the press.

The composites obtained are intended to obtain rubber consumer goods, with applications in the food industry, pharmaceutical industry, agriculture, construction, chemical industry, machine building industry, etc.

Increased demand for renewable and environmentally friendly materials, and changes in consumer preferences for environmentally friendly packaging have led to the development of biodegradable plastics. Some results regarding the obtaining of biodegradable packaging based on plasters and natural fibers have already been applied industrially both in Romania and in other countries. Studies on the production of biodegradable elastomeric materials, based on natural rubber (NR) and starch, have not been conducted so far nationally. Internationally, there is an increased interest in the use of elastomeric composites with different types of natural fibers, in several fields, due to the advantages they offer. For example, NR / Coconut fiber composites are used for Mercedes A-class seats [Deem SA, 2003, Class Coconuts: The Quest for Greener Takes Daimler Chrysler to the Rain Forest, http://popularmechanics.com/popmech/ auto3 / 0107AUTKWFBM.html], and Cordenka cellulose fibers, produced by Cordenka GmbH, are used for tire reinforcement [www.cordenka.com].

The present invention relates to the obtaining of new categories of elastomeric materials, based on natural rubber and laminated starch. Starch is an organic substance found in the seeds, fruits and tubers of plants. From a chemical composition point of view, starch is a mixture of 2 polysaccharides: amylopectin and amylose, which differ in structure and reactivity. It is made from renewable resources and has many advantages, such as: low cost, availability, non-toxic, and widely used in many areas (food, paper manufacturing, chemical, materials industry). packaging etc.) [Y. P. Wu, Q. Qi, G.-H. Liang, L.-Q. Zhang, "A strategy to prepare high performance starch / rubber composites: In sltu modlflcatlon during latex compounding process", Carbohydrate Polymers 65 (2006) 109-113],

Starch can be used as a biodegradable filler in rubber [Watcharakul, S., Umsakul, K., Hodgson, B., Chumeka, W., Tanrattanakul, V., "Biodegradation of a blended starch / natural rubber foam blopolymer and rubber gloves by Streptomyces coellcolor CH13T, Electronic Journal of Biotechnology, vol. 15, 2012, no. 1. http://dx.doi.org/10.2225/voll5-issuel-fulltext-10]. Biodegradable batches have been a topic of interest in recent years because of their potential to protect the environment by reducing non-biodegradable loads. The idea of using starch in mixtures of synthetic polymers dates back to 1969. The first studies were based on the introduction of quantities of less than 10% of starch in the synthetic matrix, keeping the granular structure intact. In this case, the starch is sensitive to enzymatic degradation, but it does not greatly affect the mechanical properties of the final material (about 20 ... 30 MPa tensile strength and

700 ... 900% elongation at break for polyethylene mixtures: starch at 90:10) [Premraj R., Mukesh Doble, "Biodegradation of polymers ¹ ', Indian Journal of Biotechnology, vol. 4, 2005, pp. 186-193],

RO 132577 Β1 in the specialized literature were identified published patents, regarding 1 obtaining composite materials with elastomeric matrix, containing starch, intended for use in various applications. The first patents refer to obtaining 3 rubber / starch mixtures in which the elastomer is used in the form of latex.

U.S. Patent No. 3480572, Starch resin reinforced rubbers, Russell A. Buchanan 5 and Charles R. Russell, Peoria, refer to the reinforcement of non-precipitated rubber latex with gelatinized or starch xanthate starch; formaldehyde and a polyhydroxyl 7 selected from the group consisting of resorcin, catechin and pyrogalol are added.

U.S. Patent No. 4005040 A, Foamed and solid rubber-starch graft copolymer 9 compositions andmethodof preparation, George G. Maher, refers to obtaining grafted copolymers with starch in aqueous medium, by the soluble xanthate solution of sodium starch with 11 a polymerizable vinyl monomer and hydrogen peroxide. They were used as a batch in rubber latexes. 13 since 1997, Goodyear Tire & Rubber Co. have obtained a number of patents:

US 5672639, 6273163, 6391945, EP 1388567 A1, wherein the starch was used in 15 tire rubber compounds, in order to improve rolling resistance, and to reduce the consumption of carbon black. 17

U.S. Patent 5672639 A, Starch composite reinforced rubber composition and tire with at least one component thereof, Filomeno Gennaro Corvasce, 19 Tom Dominique Linster, Georges Thielen, Goodyear Tire & Rubber Co, refers to a rubber composition containing a starch / plasticizer composite. , and tires having at least 21 a component of such a rubber composition. Such a component can be used for circumferential tread or other tire components. 23 The starch / plasticizer composite may be a starch and plasticizer composite, such as, for example, poly (ethylene vinyl alcohol) and / or cellulose acetate. In practice of this invention, a rubber composition comprises at least one elastomer, a starch / plasticizer composite, optionally at least one black, silica, etc. type reinforcing agent. 27

US Patent 6273163 B1, "Tire with tread of rubber composition prepared with reinforcing fillers which includes starch / plasticizer composites", Thierry Florent Edme 29 Materne, Filomeno Gennaro Corvasce, Goodyear Tire & Rubber Co, refers to the preparation of a rubber composition containing starch / plasticizer composite, together with at least one additional reinforcing agent, using a combination of an organosilane disulfide compound, mixed with a non-productive rubber composition, followed by the addition of an organosilane polysulfide compound in one step subsequent, productive. The invention also relates to the resulting rubber composition, and to their use in obtaining 35 rubber products, including tires.

US patent 6391945 B2, "Rubber containing starch reinforcement and tire 37 having component thereof", Paul Harry Sandstrom, Goodyear Tire & Rubber Co, refers to a rubber composition containing a combination of starch, modified starch 39 and / or starch composite. / plasticizer together with a selected methylene donor, and / or methylene acceptor compounds. The invention also relates to tires having at least one component composed of such a rubber composition.

EP document 1388567 A1, "Starch composite reinforced rubber composition 43 andtire withatleastonecomponentthereof ', Filomeno Gennaro Corvasce, Uwe Ernst Frank, Marc Weydert, Rene Jean Zimmer, Goodyear Tire & Rubber Co, refers to a 45 rubber composition containing at least one diene-based elastomer, a starch / plasticizer composite and maleinized polybutadiene, and tires having at least one component 47 made of such a rubber composition.

RO 132577 Β1

Then GoodyearTyre & RubberCo. used a new starch-based material, called Bio-TRED (registered trademark in 2001), to partially replace the carbon black and silica in obtaining GT3 tires, in order to reduce tire weight, and at the same time decrease energy consumption in production processes; they were used on Ford Fiesta cars.

Also in the prior art, documents US 2013/079441 A1 are found, which discloses a polymeric composite made of natural rubber mixed with starch; the starch is gelatinized with water, and as a compatibilizing agent resorcinol-formaldehyde is used, and KR 20120047435 A, which discloses the obtaining of the glycerin-coated starch, obtained by extrusion in the mixture and with other substances used for processing.

The technical problem solved by the present invention consists in establishing the optimal ratios between the raw materials, the process of obtaining, as well as the working parameters, which have the effect of obtaining polymeric composites with characteristics corresponding to obtaining rubber consumer goods, with applications. in the food, pharmaceutical, etc.

The polymer composite based on natural rubber and laminated starch, according to the invention, has in the composition: 95 ... 100 parts by weight of natural rubber, up to 5 parts by weight of natural rubber engraved with 0.1 ... 5 wt. % maleic anhydride, having double role of compatibilizer and lubricant, 0.1 ... 150 parts per 100 parts of rubber, phr, plasticizing starch reinforcing agent, up to 3 phr polyethylene glycol 4000 type compatibilizer with roll and plasticizer, up to 5 phr zinc oxide, up to 2 phr stearin, 0.1 ... 1 phr N-isopropyl-N-phenylphenylidene-diamine as antioxidant, and combinations of vulcanizing agents selected from:

5 .. .10 phrdi (tert-butylperoxy-isopropyl) benzene and up to 9 phrtrimethylpropane-trimethacrylate, or

1 .. .2.5 phr sulfur and up to 1 phr2-mercaptobenzthiazole, up to 1 phr N-cyclohexyl 2-benzylthiazyl sulfenamine, up to 1 phr tetramethylthiuramdisulfide. The laminated starch consists of

50 .. .70% starch, 30 ... 45% glycerin and optionally up to 20% water, the percentages being expressed by weight.

In the process of obtaining the polymeric composite according to the invention, the natural rubber, the plasticized starch obtained by mixing the starch, glycerin and, optionally, the water at a temperature of 70 ° C for 15 minutes at 50 ... 1000 rot / min, and auxiliary substances, the mixture can be processed on the roll with the parameters: friction 1: 1,1, a temperature of 3O ... 6O ° C, for 10 ... 25 min, or in the mixer with the parameters: speed of rotation

30 .. .60 rpm, at a temperature of 55 ... 65 ° C, for 5 ... 15 minutes; In the case of the composition processed in the mixer, this is finalized by adding the vulcanizing agents on the roller, at a friction of 1: 1.1, a temperature of 3O ... 6O ° C, for 3 ... 5 min, the final composition being processed by compression at a temperature of 150 ... 170 ° C, with a pressing force of

200 .. .300 kN, for 9 ... 16 min.

By applying the invention, the following advantages are obtained:

- decrease the toxicity of the working environment, as well as of the finished products obtained;

- lowering costs with materials;

- improvement of properties such as workability, physico-mechanical, chemical, lowering density, etc .;

- decrease of energy consumption in production processes;

- other advantages related to environmental protection as a result of replacing inorganic fillers with starch;

- The use of new compositions and green technologies will lead to a significant decrease in the rate of occupational diseases in the rubber industry, and sustainable development, by respecting EU environmental standards and reducing pollution.

RO 132577 Β1

The products according to the invention eliminate the disadvantages mentioned in the prior art, 1 in that the new polymeric composites based on natural rubber and plasticized starch totally replace the inorganic batch (with high toxicity, such as carbon black 3 or precipitated silica). with starch in the form of plasticized starch, and the compounds are obtained by the technique of mixing on the roll or in the Brabender mixer, and are processed in 5 finished products by vulcanization in the press, at high temperatures.

According to the present invention, the starch, before being introduced into the rubber mixture, is plasticized with glycerin or a mixture of glycerin and water, in different proportions. By plasticizing the starch, it is possible to improve the workability and other properties necessary for certain uses [B. Imre, B. Pukănszky, Compatibilization in bio-based and biodegradable polymer blends, European Polymer Journal 49 (2013) 1215-1233]. 11

The use of starch as a filler in the polymeric matrix offers advantages over the conventional inorganic batch, especially in terms of biodegradability and lack of toxicity, but 13 shows poor adhesion to the elastomeric matrix, because the starch is hydrophilic - contains slightly hydroxyl groups Natural rubber is 15 strong hydrophobic. This unsatisfactory interfacial adhesion between starch and natural rubber results in features not recommended for use. The improvement of the 17 mechanical properties of such composites requires a strong adhesion between the organic starch - starch and the polymeric matrix - natural rubber. For this reason, in order to 19 improve compatibility between NR and starch, appropriate compatibilizing agents will be used: 21

Maleinated natural rubber (NR-g-AM) - there are articles in the literature [Dong, Z., Liu, M., Jia, D., Y. Zhou, "Synthesis of natural rubber-g-maleic anhydride 23 andits use as a compatibilizer in natural rubber / short nylon fiber composites ”, Chin J Polym Sci (2013) 31: 1127. doi: 10.1007 / slOI18-013-1310], [Hesham Afifi, AA El-Wakil, 25 “Study of the Effect of Natural Rubber-graft-malelc Anhydride (NR-g-MA) on the Compatibility of NR-NBR Blends Using the Ultrasonic Technique ”, Journal Polymer- 27 Plastics Technology and Engineering, Vol. 47, 2008, pp. 1032-1039, http://dx.doi.org/10.1080/03602550802355271], according to which NR-g-AM 29 may be used to improve compatibility in different natural rubber mixtures with different batches or polymers. 31

Polyethylene glycol - PEG 4000 - several recent studies [Luo S., Cao J. Wang X., "Investigation of the interfacial compatibility of PEG and thermally modified wood 33 flour / polypropylene composites using the stress relaxation approach, BioResurces", 8 (2 ) 2064-2073, 2013], [Luo SP, Cao JZ, Wang X., "Properties of PEG / thermally 35 modified wood flour / polypropylene (PP) composites", Forestry Stud. China 2012; 14 (4): 307-14] have shown that PEG can be used to enhance interactions at interface 37 between hydrophilic natural fibers / polymeric-hydrophobic matrix. PEG is also used as a plasticizer for rubber. 39

The process of obtaining the composites based on natural rubber and laminated starch comprises the operations of characterization of the raw materials, dosing of the raw materials and 41 making of the composite by processing on the roll or in the Brabender type mixer. The obtained products, in the form of rubber mixtures, are presented in sheet form. These sheets of 43 mixtures of rubber by vulcanization, using molds and vulcanization presses, lead to obtaining rubber consumer goods with physical-mechanical and chemical properties 45 suitable for the field of use, low densities, low cost price, etc.

RO 132577 Β1

Polymeric composites are a mixture of the following composition: 95 ... 100 parts by weight of natural rubber, with 0 ... 5 parts by weight of natural rubber grafted with maleic anhydride (the percentage of maleic anhydride being 0.1 ... 5 wt.%), Having the dual role of compatibilizer and lubricant, 0.1 to 150 parts per 100 parts of rubber (phr) plasticizing starch reinforcing agent, 0 ... 3 phr polyethylene glycol PEG4000 type compatibilizer, which also has the role of plasticizer, 0 ... 1 phr antioxidant, vulcanizing agents and other ingredients. The cross-linking of the mixtures can be achieved with both sulfur and vulcanization accelerators, as well as with peroxides, in the presence of vulcanizing coagens.

In the following, two examples of embodiment of the invention / obtaining of the composite material based on natural rubber and plasticized starch will be presented.

Example 1

The materials used were:

- natural rubber for pharmaceutical use Crep, in the form of white rubber sheets, Mooney viscosity 67.64 ML (1 '+ 4') 100 ° C, volatile matter content 0.5%, nitrogen content 0.45 %, ash content 0.25%, impurity content 0.026%);

- potato-soluble starch (water-insoluble 0.28%, slightly biodegradable: BOD5 - 0.6 g / g - and COD -1.2 mg / g);

- glycerin: free acidity 0.02%, density 1.26 g / cm ³ , purity 99.5%;

- cross-linking agents:

- 8 parts per 100 parts of rubber (phr) peroxide of type di (tert-butylperoxypiisopropyl) benzene Perkadox 14-40B-GB (density 1.60 g / cm ³ , active oxygen content 3.8%, peroxide content 40 %);

- 3 phr trimethylpropane-trimethylacrylate crosslinker type TMPT DL 75 (ash content 22%, density 1.36 g / cm ³ , contains active agent 75 ± 3%, pH = 9.2);

- 1 phr antioxidant Richon IPPD (4010 NA) N-lzopropyl - N-phenyl - phenylenediamine, 98% purity, molecular weight 493.6374.

For plasticizing the starch, the starch (50%), the water (20%) and then the glycerin (30%) are mixed at 70 ° C for 15 minutes, at 50 ... 100 rpm. Leave for 1 h at room temperature, then in the oven 22 h at 80 ° C, and then 2 h at 110 ° C. Leave for 16 hours in a dry place for stabilization. The mixtures were obtained by the mixing technique using a roller. The way of working on the roll was:

- the natural rubber (NR) is placed on the roller and homogenized for 3 minutes;

- the antioxidant is added and mixed by mixing for 2 minutes;

- 32 phr plasticized starch is added and added, by mixing for 10 minutes;

- vulcanization agents are introduced, by mixing for 2 minutes;

- the mixture is homogenized for 3 minutes and is removed from the roll as a sheet.

Working parameters: friction of 1: 1.1 and temperature of 3O ... 5O ° C.

The rubber consumables are obtained by the compression method, using a hydraulic press.

Working parameters: temperature 165 ° C, pressing force 300 kN and vulcanization time 16 min.

The physical-mechanical properties of the composites obtained depend on the amount of plasticized starch introduced into the rubber mixture, as follows: the hardness increases, the elasticity decreases, and the breaking resistance and the tear resistance vary unevenly with increasing the amount of plasticized starch in the mixture.

RO 132577 Β1

The physical-mechanical characteristics determined for the composites based on natural rubber 1 and starch, obtained on the roll and vulcanized with peroxide and vulcanization coagent presented, are the following: 3

- hardness: 48 ° ShA;

- elasticity: 40%; 5

- breaking strength: 6,8 N / mm ² ;

- elongation at break: 560%; Ί

- density: 1.09 g / cm ² ;

- tear resistance: 19,5 N / mm; 9

- variation of mass in water after 22 h: 8.48%.

Example 211

The materials used were similar to those presented in Example 1, and in addition were used: 13

- maleic anhydride for synthesis (melting temperature 52 ° C), for maleinization of natural rubber;

- polyethylene glycol PEG 4000 (density 1,128 g / cm ³ , mp 4 ... 8 ° C);

- curing agents: 17

- sulfur - 99.5% sulfur content, mp 117 ° C, ash content

0.1% 19

- 2 mercaptobenzthiazole (MBT) - molecular weight 167.2, melting point

179 ° C, density 1.42 g / cm ³ ; 21

- N-cyclohexyl 2-benzylthiazyl sulfenamine (CBS) - molecular weight 264.4, m.p. 101 ° C, density 1.31 g / cm ³ ; 23

- tetramethylthiuramdisulfide (TMTD) - molecular mass 240.4, melting point

156 ° C, density 1.43 g / cm ³ .25

Vulcanizing activators: zinc oxide grade I and stearin.

For plasticizing the starch, the starch (65%) is mixed with glycerin (35%) for 27 7 minutes at 1000 rpm and 70 ° C, until a homogeneous mixture is obtained. Leave for 16 hours in a dry place for stabilization. The maleinized rubber (NR-g-AM) was obtained by mixing on the roll of natural rubber with 5 phr maleic anhydride and 0.75 phr di (tert-butyperoxy-isopropyl) benzene. The sheet of natural rubber mixture with maleic anhydride was used after holding for 1 h at 160 ° C, and then stabilizing at room temperature for about 16 h.

The mixtures were obtained by mixing technique on the Brabender mixer.

The working method for the mixer was: 35

- the natural rubber (NR) and the natural maleinized rubber (NR-g-AM) are inserted into the mixer and are plasticized to a constant torque value for 37 2 minutes;

- 60 phr plasticized starch is added and added for 4 minutes;

- 5 phr zinc oxide, 1 phr stearin, 3 phr polyethylene glycol PEG 4000 and 1 phr antioxidant are added and added to the mixture by mixing for 2 min; 41

- it is homogenized - about 1 min at constant torque.

Working parameters: rotation speed 30/60 rpm, temperature 60 ± 5 ° C.43

Vulcanizing agents: 1.5 phr sulfur and vulcanization accelerators (0.5 phr each) are included on the roll: friction 1: 1.1, temperature 3O ... 5O ° C and working time 4 min. 45 The mixture is removed from the roll as a sheet. The rubber consumables are obtained by the compression method, using a hydraulic press. Working parameters: temperature 165 ° C, 47 pressing force 300 kN and vulcanization time of 9 min.

RO 132577 Β1

The physico-mechanical properties of the composites obtained depend on the amount of plasticized starch introduced into the rubber mixture, as follows:

- the hardness increases and the elasticity decreases as a result of the increased amount of plasticized starch in the mixture, indicating that this can lead to the reinforcement of the rubber mixture, thus replacing the inorganic band;

- the introduction of large quantities of plasticized starch (90 ... 150 phr) leads to a decrease of the breaking and breaking resistance, but the physical-mechanical and chemical properties are maintained at values suitable for applications for the food and pharmaceutical industry.

The physical-mechanical and chemical characteristics determined for the composites based on natural rubber and starch are as follows:

- hardness: 48 ° ShA;

- elasticity: 30%;

- breaking strength: 7,2 N / mm ² ;

- elongation at break: 780%;

- density: 1.06 g / cm ² ;

- tear resistance: 14 N / mm;

- variation of mass after immersion 22 h in: water of 10.04%, in ethyl alcohol of 10.50%, in sunflower oil of 15.30%, in solution 5% glucose of 2.54%, in solution 0.9% 15.05% sodium chloride.

Claims (3)

Claims 1 1. Polymeric composite based on natural rubber and laminated starch, characterized in that it has: 95 ... 100 parts by weight of natural rubber, up to 5 parts by weight of natural rubber engraved with 0.1 ... 5 wt.% maleic anhydride, having double role of 5 compatibilizer and lubricant, 0.1 ... 150 parts per 100 parts of rubber, phr, plasticized starch reinforcing agent, up to 3 phr polyethylene glycol 4000 type compatibilizer, with a role and 7 plasticizers, up to 5 phr zinc oxide, up to 2 phr stearin, 0.1 ... 1 phr N-isopropyl-Nphenyl-phenylidene-diamine with antioxidant role, and combinations of selected vulcanizing agents 9 of: 5 ... 10 phr di (tert-butylperoxy-isopropyl) benzene and up to 9 phr trimethylpropantrimethacrylate, or 1 ... 2,5 phr sulf and up to 1 phr 2-mercaptobenzthiazole, up to 1 phr 11 N -cyclohexyl 2-benzylthiazyl sulfenamine, up to 1 phr tetramethylthiuramdisulfide. 2. Polymeric composite according to claim 1, characterized in that the laminated starch 13 is made up of 50 ... 70% starch, 30 ... 45% glycerin and optionally up to 20% water, the percentages being expressed by weight. 15 3. The process for obtaining the polymeric composite defined in claim 1, characterized in that the natural rubber, the plasticized starch obtained by mixing the starch, glycerin and optionally water at a temperature of 70 ° C is mixed, during 15 min, at 50 ... 1000 rpm, and auxiliary substances, the mixture can be processed on a roll 19 parameters: friction 1: 1,1, a temperature of 3O ... 6O ° C, for 10 ... 25 min, or in the mixer with the parameters: rotation speed 30 ... 60 rot / min, at a temperature of 55 ... 65 ° C, for 5 ... 15 min; 21 in the case of the composition processed in the mixer, this is finalized by adding vulcanizing agents on the roller, at a friction of 1: 1.1, a temperature of 3O ... 6O ° C, for 3 ... 5 min, 23 the final composition being processed by compression at a temperature of 150 ... 170 ° C, with a pressing force of 200 ... 300 kN, for 9 ... 16 min. 25