The order of the PP packaging material market made it difficult for other plastic packaging materials. In recent years, the use of chemical additives for fine chemical products has been effectively modified to make the characteristics of PP materials not only closer to the value of several times higher than the performance index of PET, but also printability and ink film. Adhesion, strength, transparency, gloss, moisture resistance, air tightness, etc. are all superior to traditional PET.
The development of PP resin in China began in the 1950s. After more than 40 years of production and application, it has been used as an alternative packaging material for paper, metal, wood, etc., especially after more than ten years of research, its application scope is more extensive. Through the modification of additives, products such as secondary and tertiary coating, composite packaged physical goods, and heat-shrinkable silk screen packaging can be seen everywhere, becoming the first favorite of plastic packaging materials. It is estimated that by 2010, the annual consumption will exceed 2 million tons.
With the continuous expansion of the use of PP packaging materials, its defects have become increasingly apparent. Some companies use two-way stretch film packaging after storage for a period of time, the emergence of fog, sweating, the production of plastic barrels blackened, PP woven bag of fiber broken powder and other phenomena. Through research, it has been found that plastic additives are the key factors to improve the packaging materials. In view of the different defects of PP packaging materials, selecting different additives and dosages to improve its performance is still a subject of research in the packaging industry.
I. The defects of PP and its causes and solutions.
1.PP electrical insulation
After being rubbed, the PP film is prone to static electricity, which often leads to the adsorption of dust on the surface and affects the appearance and transparency. The elimination method is:
1 Adding an antistatic agent to the ingredients; usually use a nonionic antistatic agent with a very low polarity.
2 Print or spray antistatic agent on its surface. For example, the amphoteric surfactant can not only prevent static electricity, but also reduce the contact surface of water, thereby improving the hydration sprayability of the PP film.
2. Synthesis of highly crystalline HCPP with high activity catalyst
For example, when a biaxially oriented film is used, its modulus increases by about 10% to 20%, and the thermal shrinkage can also be greatly reduced. In addition, this kind of film has high crystallization rate, small deformation and high hardness, so it is comparable to ABS, and it is one of the cheapest materials to replace PET material for commodity packaging.
3.PP decorative
The decorative effect obtained by the traditional PP dyeing printing technology can no longer meet people's daily life requirements and artistic requirements (uniform color space). If organic solvents and surfactants are used, the stress cracking of PP can be significantly promoted, but the stress cracking resistance of PP tends to increase with the increase of the molecular weight, and also depends on the catalyst residual amount and the antioxidant system. Therefore, when the surface is subjected to secondary or tertiary processing and regeneration multiplexing, a blunt catalyst must be added. If electroplating, film attachment, lamination, hot stamping of gold and silver, and printing of graphics and other means are used, the fog generated by the PP film will be greatly eliminated, making up for the lack of packaging and decoration, so that the PP reaches a beautiful surface and a certain degree of Hardness glossy film.
4.PP heat resistance
A more practical ladder polymer and helical polymer recently developed are non-crosslinked structures in which two molecular chains are twisted with each other, such that PP is soluble and is more common than ordinary The structured PP has better thermal properties. This is followed by the use of Ziegler catalysts to produce isotactic polypropylene with a melting point of up to 300°C. There are also selected compatibility parameters and similar two or more high molecular polymers grafted and blended to achieve the intended heat resistance. At present, zinc stearate, calcium, and barium are mostly used. Long-acting MW300-1200 molecular weight has also recently been selected as a heat stabilizer.
5.PP's aging resistance
The usual practice is to add antioxidants and UV absorbers and copper inhibitors (CY2NO×2379) to the PP material. The 141 compound antioxidant recently put on the market is a plastic additive that is more suitable for PP materials. Light source is a very important factor in PP aging. The most common solar spectrum in nature is generally divided into:
1 ultraviolet region (wavelength 290 ~ 400nm), accounting for 4%;
2 visible light area (wavelength 400 ~ 700nm), accounting for 43%;
3 infrared (wavelength 700 ~ 2500nm), accounting for 53%. Although the ultraviolet energy only accounts for 4% of the solar energy, PP packaging materials are damaged in the ultraviolet region because PP films, sheets, braided yarns, etc. will age at 330-370 nm.
6. Chemical resistance and wear resistance
PP is likely to cause resistance to the outside of the system after exposure to chemicals, and its quality will be damaged (such as water, solvents, acids, alkalis, etc.). For example, some biaxially stretched PP films produced by plastic film factories will inevitably come into contact with moist air or moisture during the practical application of cigarettes, plus the erosion of nicotine and the volatilization of solvents in composite adhesives. The expansion of the packaging mask and water permeability, air permeability, water vapor, PP biaxially stretched film will occur blistering, discoloration, spray, sweating, bleaching, fog and other phenomena, which directly affect the life of the product, so that cigarettes Resist mildew.
7. Another major factor affecting the quality of packaging is transparency.
In order to accelerate the crystallization of PP, the crystal structure of the surface of the product is uniform, and a fine spherulite structure is formed. Usually 0.01 to 0.05% of DBS nucleating agent and antimony trioxide anti-flame retardant and the like are added. The stretching (orientation) of PP means that the free surface of its internal structural units (such as molecules or grains, etc.) must follow some preferred direction rather than being totally random. Because it gets a certain degree of orientation when it flows and deforms. The orientation state reflects the molecular aggregation structure. However, its performance is anisotropic. Properly adjusting the orientation conditions can vary the properties and uses of PP stretched films in a wide range - fibers, monofilaments, flat yarns, narrow-band orientations and tear films. Below the melting point, the stretching orientation above the glass transition temperature is not stable, but the progressive cooling crystallinity is relatively high, and is correspondingly stable. For example, it can be transformed into a monoclinic crystal at 70° C.; only half of the transformation occurs at 110° C.; At 145°C, most of the transformation occurs, whereas monoclinic crystals begin to melt at 170°C. The production always involves the extrusion and drawing orientation of the sheet together because the stretching temperature is set at the maximum rate of crystallization at the temperature and the melting point. Between -120 and 150°C. Although ordinary PP can greatly improve weatherability and transparency, branching degree, and gloss retention after adding a nucleating agent, it is more important that the crystallization rate in the PP system doubles. As the number of crystal growth increases in the same system and the size of the crystal decreases, the result is that the crystal is smaller than the wavelength of visible light to allow light to pass through, thereby enhancing the transparency and greatly reducing the surface defects of its products. However, the effective temperature of domestically produced SKG-Y5988 is 185 to 260°C. In actual use, it is necessary to mix and disperse the PP resin after it is dispensed. Otherwise, the purpose of adding an organic nucleating agent cannot be achieved.
Secondly, the draw ratio is about 7 in the stretch orientation process. Stretch ratio There is also a problem of control of the ambient humidity and stretching temperature of the shop. Although the strength of the article can be increased at a high draw ratio, the residual elongation becomes smaller and the transparency is affected.
Second, the application of additives
Practice in recent years has proved that: Without packaging materials without additives, their application scope and application methods have become a hot topic for packaging companies. For example, PP biaxially stretched oriented films, in the presence of stabilizers, destroy the formation of alkene structures, thereby inhibiting discoloration of the PP - especially from white to gray again. Another example is the thermal oxygen stabilization, light stabilization, and the catalysis of passivating metal ions. Thermal oxygen stabilization is the most important of these problems. The function and amount of additives are described below:
Stabilizer
1 organic salts, organic tin, and pure organic compounds in stabilizers are divided into: long-acting heat stabilizers, generally in an amount of 1 to 3%, mainly using the molecular weight of MW300N-1200; zinc stearate, calcium stearate Strontium stearate, etc.
2 light stabilizer: The amount of 0.01 to 0.05% UV absorber OV-P, UV-326, UV-327 and so on.
3 main antioxidant: The amount of 0.1 to 0.5%, the use of DSTP to make the white turbidity trend of PP (that is, sulfide esters); can also use tetradecyl ester or Szndunovr3212 can be added to improve the oxygen with the metal ink.
4 Biocides: The dosage is 0.1 to 0.2%. There are more than 300 kinds of chemicals used for anti-microbial erosion, but there is no successful report on PP materials.
5 other: such as light shielding agent, quencher, free radical agent and so on.
2. Characteristic additives
1Features Additives: The dosage is 100～30%. The inorganic and organic fillers, such as calcium, wood flour, white carbon black, talcum powder, etc.
2 enhancer: The amount of 10 to 40%, mica, wollastonite, carbon fiber and so on.
3 coupling agent: often referred to as modifier, the amount of 0.1 to 5%. Commercially available and divided: silicon, organosilanes, organic zirconium esters, etc.; titanium: organic titanates, organic aluminates; phosphate esters.
4 plasticizers and reactive plasticizers: The amount of 0.1 to 1%. Monomer molecular weight is between 200-600. The polymerization type is between 1000 and 8000. It is generally divided into industrial phosphate esters, phthalic acid esters, aliphatic dibasic acid esters, epoxy compounds, polyesters, chlorine-containing compounds, and allbenzenes. Formic acid esters, trioctyl trimellitate and other 11 series. However, most of the PP materials used are phthalate or polyvinyl chloride resins.
5 coloring agent: inorganic and Organic Pigment dyes, etc., the amount of 30 to 0.8% (brighteners, titanium dioxide, phthalocyanine blue, benzidine yellow, plastic red, etc.).
6 impact modifier: The amount of 1 to 10%, while most of the PP using polybutadiene and olefin (PE) thermoplastic elastomer to improve the PP sheet or film tear strength and anti-brittleness.
7 flame retardant: It is divided into: add type and reaction type. The dosage is 0.1-0.5%. Such as inorganic aluminum hydroxide, antimony trioxide and organic polymer flame retardant resin, such as polyvinyl chloride. 8 anti-static agent, the general amount of 1 to 15%.
3. Processing additives
Processing additives are generally 0.05 to 0.25%, while PP films are rarely used. Usually divided into:
1 blowing agent. There are physical foaming agents, generally choose low-boiling alcohols, ethers, ketones and aromatic hydrocarbons; chemical foaming agents, such as sodium bicarbonate, AC and so on.
2 lubricant: The amount of 0.01 ~ 0.1%, often fatty amides and hydrocarbons, etc., the agent can often be added to the printing ink film surface, so the use of caution.
3 processing release agent: The amount of 0.01 to 0.1%. PP materials often use organosilicon compounds, fluoropolymers, and polyethylene waxes as the first choice.
4 Anti-blocking agents: The traditional method is to add talc when cutting, but often leads to excessive dust and pollute the workshop environment. Most of the fatty acid metal salts are introduced into the PP film system.
5 slip agent: often low-cost talcum powder as a post-print additive, now more use of oil, erucic acid organic additives directly in the PP ingredients added.
6Compatibilizer: PCL and CPE, which are often regarded as the third component, can be used in the PP system.
7 Assigning Agent: P-type that can be applied to PP is preferable.
8 Tackifiers: Acrylics suitable for PP packaging printing: Dimerum rosin (softening point 145°C) and poly (B-pinene) terpene resin (softening point 115°C).
9 Neutral superdispersants to be explored.
4. Reaction control
The dosage is often controlled between 1 and 5%.
1 Catalyst: A system composed mostly of TiCl4 or TiCl3 or AlC2H5)3. This is a class of substances that can change the speed of a chemical reaction without itself being consumed in the reaction. So far PP has not found one of the most effective additives and stereotypes.
2 Initiator: Although its role is different from that of the catalyst, there is no complete theory to explain the PP application.
3 polymerization inhibitor: The purpose is to remove the PP prior to polymerization, so as to avoid the induction period after the occurrence of the phenol, anthraquinone and other additives.
4 Cross-linking agent: Dicumyl peroxide is commonly used in PP materials.
5 mildew inhibitor: pentachlorobenzene
The development of PP resin in China began in the 1950s. After more than 40 years of production and application, it has been used as an alternative packaging material for paper, metal, wood, etc., especially after more than ten years of research, its application scope is more extensive. Through the modification of additives, products such as secondary and tertiary coating, composite packaged physical goods, and heat-shrinkable silk screen packaging can be seen everywhere, becoming the first favorite of plastic packaging materials. It is estimated that by 2010, the annual consumption will exceed 2 million tons.
With the continuous expansion of the use of PP packaging materials, its defects have become increasingly apparent. Some companies use two-way stretch film packaging after storage for a period of time, the emergence of fog, sweating, the production of plastic barrels blackened, PP woven bag of fiber broken powder and other phenomena. Through research, it has been found that plastic additives are the key factors to improve the packaging materials. In view of the different defects of PP packaging materials, selecting different additives and dosages to improve its performance is still a subject of research in the packaging industry.
I. The defects of PP and its causes and solutions.
1.PP electrical insulation
After being rubbed, the PP film is prone to static electricity, which often leads to the adsorption of dust on the surface and affects the appearance and transparency. The elimination method is:
1 Adding an antistatic agent to the ingredients; usually use a nonionic antistatic agent with a very low polarity.
2 Print or spray antistatic agent on its surface. For example, the amphoteric surfactant can not only prevent static electricity, but also reduce the contact surface of water, thereby improving the hydration sprayability of the PP film.
2. Synthesis of highly crystalline HCPP with high activity catalyst
For example, when a biaxially oriented film is used, its modulus increases by about 10% to 20%, and the thermal shrinkage can also be greatly reduced. In addition, this kind of film has high crystallization rate, small deformation and high hardness, so it is comparable to ABS, and it is one of the cheapest materials to replace PET material for commodity packaging.
3.PP decorative
The decorative effect obtained by the traditional PP dyeing printing technology can no longer meet people's daily life requirements and artistic requirements (uniform color space). If organic solvents and surfactants are used, the stress cracking of PP can be significantly promoted, but the stress cracking resistance of PP tends to increase with the increase of the molecular weight, and also depends on the catalyst residual amount and the antioxidant system. Therefore, when the surface is subjected to secondary or tertiary processing and regeneration multiplexing, a blunt catalyst must be added. If electroplating, film attachment, lamination, hot stamping of gold and silver, and printing of graphics and other means are used, the fog generated by the PP film will be greatly eliminated, making up for the lack of packaging and decoration, so that the PP reaches a beautiful surface and a certain degree of Hardness glossy film.
4.PP heat resistance
A more practical ladder polymer and helical polymer recently developed are non-crosslinked structures in which two molecular chains are twisted with each other, such that PP is soluble and is more common than ordinary The structured PP has better thermal properties. This is followed by the use of Ziegler catalysts to produce isotactic polypropylene with a melting point of up to 300°C. There are also selected compatibility parameters and similar two or more high molecular polymers grafted and blended to achieve the intended heat resistance. At present, zinc stearate, calcium, and barium are mostly used. Long-acting MW300-1200 molecular weight has also recently been selected as a heat stabilizer.
5.PP's aging resistance
The usual practice is to add antioxidants and UV absorbers and copper inhibitors (CY2NO×2379) to the PP material. The 141 compound antioxidant recently put on the market is a plastic additive that is more suitable for PP materials. Light source is a very important factor in PP aging. The most common solar spectrum in nature is generally divided into:
1 ultraviolet region (wavelength 290 ~ 400nm), accounting for 4%;
2 visible light area (wavelength 400 ~ 700nm), accounting for 43%;
3 infrared (wavelength 700 ~ 2500nm), accounting for 53%. Although the ultraviolet energy only accounts for 4% of the solar energy, PP packaging materials are damaged in the ultraviolet region because PP films, sheets, braided yarns, etc. will age at 330-370 nm.
6. Chemical resistance and wear resistance
PP is likely to cause resistance to the outside of the system after exposure to chemicals, and its quality will be damaged (such as water, solvents, acids, alkalis, etc.). For example, some biaxially stretched PP films produced by plastic film factories will inevitably come into contact with moist air or moisture during the practical application of cigarettes, plus the erosion of nicotine and the volatilization of solvents in composite adhesives. The expansion of the packaging mask and water permeability, air permeability, water vapor, PP biaxially stretched film will occur blistering, discoloration, spray, sweating, bleaching, fog and other phenomena, which directly affect the life of the product, so that cigarettes Resist mildew.
7. Another major factor affecting the quality of packaging is transparency.
In order to accelerate the crystallization of PP, the crystal structure of the surface of the product is uniform, and a fine spherulite structure is formed. Usually 0.01 to 0.05% of DBS nucleating agent and antimony trioxide anti-flame retardant and the like are added. The stretching (orientation) of PP means that the free surface of its internal structural units (such as molecules or grains, etc.) must follow some preferred direction rather than being totally random. Because it gets a certain degree of orientation when it flows and deforms. The orientation state reflects the molecular aggregation structure. However, its performance is anisotropic. Properly adjusting the orientation conditions can vary the properties and uses of PP stretched films in a wide range - fibers, monofilaments, flat yarns, narrow-band orientations and tear films. Below the melting point, the stretching orientation above the glass transition temperature is not stable, but the progressive cooling crystallinity is relatively high, and is correspondingly stable. For example, it can be transformed into a monoclinic crystal at 70° C.; only half of the transformation occurs at 110° C.; At 145°C, most of the transformation occurs, whereas monoclinic crystals begin to melt at 170°C. The production always involves the extrusion and drawing orientation of the sheet together because the stretching temperature is set at the maximum rate of crystallization at the temperature and the melting point. Between -120 and 150°C. Although ordinary PP can greatly improve weatherability and transparency, branching degree, and gloss retention after adding a nucleating agent, it is more important that the crystallization rate in the PP system doubles. As the number of crystal growth increases in the same system and the size of the crystal decreases, the result is that the crystal is smaller than the wavelength of visible light to allow light to pass through, thereby enhancing the transparency and greatly reducing the surface defects of its products. However, the effective temperature of domestically produced SKG-Y5988 is 185 to 260°C. In actual use, it is necessary to mix and disperse the PP resin after it is dispensed. Otherwise, the purpose of adding an organic nucleating agent cannot be achieved.
Secondly, the draw ratio is about 7 in the stretch orientation process. Stretch ratio There is also a problem of control of the ambient humidity and stretching temperature of the shop. Although the strength of the article can be increased at a high draw ratio, the residual elongation becomes smaller and the transparency is affected.
Second, the application of additives
Practice in recent years has proved that: Without packaging materials without additives, their application scope and application methods have become a hot topic for packaging companies. For example, PP biaxially stretched oriented films, in the presence of stabilizers, destroy the formation of alkene structures, thereby inhibiting discoloration of the PP - especially from white to gray again. Another example is the thermal oxygen stabilization, light stabilization, and the catalysis of passivating metal ions. Thermal oxygen stabilization is the most important of these problems. The function and amount of additives are described below:
Stabilizer
1 organic salts, organic tin, and pure organic compounds in stabilizers are divided into: long-acting heat stabilizers, generally in an amount of 1 to 3%, mainly using the molecular weight of MW300N-1200; zinc stearate, calcium stearate Strontium stearate, etc.
2 light stabilizer: The amount of 0.01 to 0.05% UV absorber OV-P, UV-326, UV-327 and so on.
3 main antioxidant: The amount of 0.1 to 0.5%, the use of DSTP to make the white turbidity trend of PP (that is, sulfide esters); can also use tetradecyl ester or Szndunovr3212 can be added to improve the oxygen with the metal ink.
4 Biocides: The dosage is 0.1 to 0.2%. There are more than 300 kinds of chemicals used for anti-microbial erosion, but there is no successful report on PP materials.
5 other: such as light shielding agent, quencher, free radical agent and so on.
2. Characteristic additives
1Features Additives: The dosage is 100～30%. The inorganic and organic fillers, such as calcium, wood flour, white carbon black, talcum powder, etc.
2 enhancer: The amount of 10 to 40%, mica, wollastonite, carbon fiber and so on.
3 coupling agent: often referred to as modifier, the amount of 0.1 to 5%. Commercially available and divided: silicon, organosilanes, organic zirconium esters, etc.; titanium: organic titanates, organic aluminates; phosphate esters.
4 plasticizers and reactive plasticizers: The amount of 0.1 to 1%. Monomer molecular weight is between 200-600. The polymerization type is between 1000 and 8000. It is generally divided into industrial phosphate esters, phthalic acid esters, aliphatic dibasic acid esters, epoxy compounds, polyesters, chlorine-containing compounds, and allbenzenes. Formic acid esters, trioctyl trimellitate and other 11 series. However, most of the PP materials used are phthalate or polyvinyl chloride resins.
5 coloring agent: inorganic and Organic Pigment dyes, etc., the amount of 30 to 0.8% (brighteners, titanium dioxide, phthalocyanine blue, benzidine yellow, plastic red, etc.).
6 impact modifier: The amount of 1 to 10%, while most of the PP using polybutadiene and olefin (PE) thermoplastic elastomer to improve the PP sheet or film tear strength and anti-brittleness.
7 flame retardant: It is divided into: add type and reaction type. The dosage is 0.1-0.5%. Such as inorganic aluminum hydroxide, antimony trioxide and organic polymer flame retardant resin, such as polyvinyl chloride. 8 anti-static agent, the general amount of 1 to 15%.
3. Processing additives
Processing additives are generally 0.05 to 0.25%, while PP films are rarely used. Usually divided into:
1 blowing agent. There are physical foaming agents, generally choose low-boiling alcohols, ethers, ketones and aromatic hydrocarbons; chemical foaming agents, such as sodium bicarbonate, AC and so on.
2 lubricant: The amount of 0.01 ~ 0.1%, often fatty amides and hydrocarbons, etc., the agent can often be added to the printing ink film surface, so the use of caution.
3 processing release agent: The amount of 0.01 to 0.1%. PP materials often use organosilicon compounds, fluoropolymers, and polyethylene waxes as the first choice.
4 Anti-blocking agents: The traditional method is to add talc when cutting, but often leads to excessive dust and pollute the workshop environment. Most of the fatty acid metal salts are introduced into the PP film system.
5 slip agent: often low-cost talcum powder as a post-print additive, now more use of oil, erucic acid organic additives directly in the PP ingredients added.
6Compatibilizer: PCL and CPE, which are often regarded as the third component, can be used in the PP system.
7 Assigning Agent: P-type that can be applied to PP is preferable.
8 Tackifiers: Acrylics suitable for PP packaging printing: Dimerum rosin (softening point 145°C) and poly (B-pinene) terpene resin (softening point 115°C).
9 Neutral superdispersants to be explored.
4. Reaction control
The dosage is often controlled between 1 and 5%.
1 Catalyst: A system composed mostly of TiCl4 or TiCl3 or AlC2H5)3. This is a class of substances that can change the speed of a chemical reaction without itself being consumed in the reaction. So far PP has not found one of the most effective additives and stereotypes.
2 Initiator: Although its role is different from that of the catalyst, there is no complete theory to explain the PP application.
3 polymerization inhibitor: The purpose is to remove the PP prior to polymerization, so as to avoid the induction period after the occurrence of the phenol, anthraquinone and other additives.
4 Cross-linking agent: Dicumyl peroxide is commonly used in PP materials.
5 mildew inhibitor: pentachlorobenzene
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