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The hardness of common rubber roller

printing and dyeing roller
Name of rubber roller	Rubber roller hardness (Shore A)	Rubber roller material
printing rubber roller	92~97	chlorosulfonation of nitrile
Roller	80~85	chlorosulfonation of nitrile
pad dyeing roll	85~90	chlorosulfonation of nitrile
hollow bending roll	55~60	Nitrile
Flat wash roll	100	Nitrile
Flat wash lower roll	80	Nitrile
offset roller
Name of rubber roller	Rubber roller hardness (Shore A)	Rubber roller material
Ink roller	20~25	Nitrile
mimeograph roller	25~30	Nitrile
offset roller	30~35	Nitrile
printing roll	40~45	Nitrile
High Speed Flat Roller	25~30	Nitrile
Paper roll
Name of rubber roller	Rubber roller hardness (Shore A)	Rubber roller material
Roller	85~95	Natural, butylbenzene, cis-butyl
Squeeze roll	75~85	Natural, butylbenzene, cis-butyl
Press roll	80~90	Natural, butylbenzene, cis-butyl
Blanket roll	95~100	Natural, butylbenzene, cis-butyl
Case roller	95~100	Natural, butylbenzene, cis-butyl
wool roll	95~100	Natural, butylbenzene, cis-butyl
vacuum roll	80~90	Natural, butylbenzene, cis-butyl
breast roll	70~80	Natural, butylbenzene, cis-butyl
Mesh roll	30~35	Natural, butylbenzene, cis-butyl
Other Cots
Name of rubber roller	Rubber roller hardness (Shore A)	Rubber roller material
leather roller	50~60	Silicone, butyl, ethylene propylene rubber
husking roller	90~100	Nitrile
Belt conveyor idler	70~80	Styrene-butadiene
Typewriter roll	85~90	Nitrile
press slurry roll	60~65	Food grade material
Banknote counter silicone roller	55~75	Silicone

 

Rubber Name	Application Industry	Main advantages
NR natural rubber	Printing, woodworking, papermaking, printing and dyeing	1. Good elasticity 2. Good wear resistance 3. High mechanical strength 4. Good alkali resistance, but not strong acid resistance. 5. Maximum working temperature 80 ℃
SBR styrene-butadiene rubber	Papermaking, printing and dyeing, printing	1. Good aging resistance 2. Good abrasion resistance 3. Good tensile strength, resistance to non-polar solvents 4. Low elasticity and poor hot tear performance
CR neoprene	Papermaking, printing and dyeing, printing	1. Excellent aging resistance 2. Good oil resistance and solvent resistance 3. Excellent flame retardancy 4. Resistance to non-polar solvents and good chemical corrosion resistance. Except for strong oxidizing acids, other acids and bases have almost no effect on them.
EPDM EPDM	Printing, paper UV ink	1. Good aging resistance 2. Good heat resistance 3. High elasticity 4. Great resistance to alcohol, acid, strong alkali, oxidant, ketone and some esters, but poor resistance to gasoline, benzene, xylene and other solvents
NBR nitrile rubber	Printing	1. Good oil resistance 2. Wear resistance is 30% to 50% higher than NR 3. Good heat resistance, but not resistant to ozone 4. Excellent resistance to non-polar and weak polar oils and solvents, but poor resistance to aromatic and chlorinated hydrocarbon oils
Q Silicone Rubber	compound film	1. Excellent high and low temperature resistance 2. Excellent ozone resistance, oxygen resistance, light resistance and weathering resistance 3. Has certain resistance to low concentration of acid and alkali, and has good resistance to ethanol and acetone 4. Low strength and poor wear resistance, with a maximum temperature resistance of 250 ℃
CSM chlorosulfonated polyethylene rubber	Steel	1. Excellent aging resistance 2. Good wear resistance, good physical and mechanical properties 3. Excellent ozone resistance 4. The highest temperature resistance is 150 ℃ 5. Oil resistance is not as good as CR and NBR.
PU polyurethane	Rubber, steel, aluminum, paper	1. good elasticity 2. two kinds of solvent resistance and wear resistance, respectively, with better wear resistance and better oil resistance characteristics 3. oxygen, ozone, and ultraviolet radiation effect performance is good 4. no acid, alkali
fluorine rubber roller	Coating	With high heat resistance, oil resistance, acid and alkali resistance, air permeability resistance, electrical insulation, aging resistance, flame resistance, wear resistance and other properties are also very good, for special coating equipment.
butyl rubber roller	Chemical	High resistance to chemical solvents, good heat resistance (170 ℃), excellent acid and alkali resistance, suitable for color printing machinery, tanning machinery, coating equipment, etc.

 

rubber molding process

 

01

 

Basic Key Points of Formula Design

The rubber roller should have accurate and uniform surface hardness, and the vulcanized rubber is required to have good self-adhesive properties. It is also very important to select suitable raw rubber varieties and compounding agents. The following points should be paid attention.

(1) Cots are thick products. The thickness of the adhesive layer is generally between 20 and 25mm, and there are special requirements for thickening to about 40mm. When considering the western countries, full attention should be paid to the formula design principles of thick products, and a longer flat vulcanization curve is required to adapt to the characteristics of low temperature and long time vulcanization.

(2) adjustment of the compounding agent. In the formulation of hard rubber, slaked lime is used as an inorganic accelerator to avoid over-sulfur and embrittlement of hard rubber. If it is used together with accelerator DM, the performance is better. The amount of softener should not be too much, should avoid the use of easy to spray out of petroleum alkanes, otherwise easy to produce delamination phenomenon.

(3) vulcanizing agent. The use of high-quality sulfur powder can avoid uneven and insufficient hardness.
 

01

Rubber preparation

 

For the rubber roller, the mixing of the rubber material is the most critical link. The types of rubber materials used for rubber rollers range from natural rubber, synthetic rubber to more than 10 kinds of special materials, with a rubber content of 25% ~ 85% and a hardness of soil (0~90) degrees, spanning a great range. Therefore, how to make these compounds uniformly mixed has become a major problem. The regular method is to use an open mill to mix and process in the form of a variety of masterbatches. In recent years, companies have switched more to meshing internal mixers to produce rubber in a segmented mixing manner.

After the rubber material is uniformly mixed, the rubber filter shall be used to filter the rubber material to eliminate the impurities in the rubber material. Then, calender, extruder and laminating machine are used to make film or rubber strip without bubbles and impurities for rubber roller molding. Before molding, these films and strips should be strictly inspected in appearance to limit the storage period, maintain a fresh surface and prevent adhesion and extrusion deformation. Because most of the rubber rollers are non-molded products, once there are impurities and bubbles on the surface of the rubber, sand holes may occur when the surface is ground after vulcanization, which will lead to excessive repair or even scrap of the entire rubber roller.
 

02

Molding

Roller molding is mainly in the metal core paste coated rubber, there are package paste method, extrusion method, molding method, injection pressure method and injection method. At present, the main domestic mechanical or manual paste molding, most of the foreign countries have achieved mechanical automation. Large and medium-sized rubber rollers are basically produced by profiling extrusion, continuous paste molding with extruded film or continuous winding molding of extruded rubber strips. At the same time, in the molding process to the microcomputer automatic control of its size and appearance shape, some can also be used to press the machine right angle and shaped extrusion method for molding.

The above molding method can not only reduce the labor intensity, but also eliminate the possible bubbles. In order to prevent the deformation of the rubber roller during vulcanization and to prevent the generation of bubbles and sponges, especially for the rubber roller formed by the wrapping method, the external flexible pressure method is also adopted. Usually, several layers of cotton or nylon cloth are wrapped around the outer surface of the rubber roller, and then fixed and pressurized with steel wire or fiber rope. Although this process has long been mechanized, the manufacturing process is complicated by the fact that the bandage is removed after vulcanization to form a "cecum" process, and the use of the bandage and winding rope is extremely limited and the consumption is large.

For small and micro rubber rollers, various production processes such as manual patch, extrusion, injection, injection and pouring can be used. In order to improve production efficiency, the molding method is now mostly used, and the accuracy is much higher than that of the non-molding method. Solid rubber injection pressure, injection and liquid rubber pouring, has become the main mode of production.

 

03

vulcanization

 

At present, the vulcanization method of large and medium-sized rubber rollers is still vulcanization tank vulcanization. Although the flexible pressurization mode has changed, it is still not separated from the heavy labor burden of transportation and lifting. The vulcanization heat source has three heating methods: steam, hot air and hot water, and the mainstream is still steam. Due to the metal core contact with water vapor and special requirements of the roller, the use of indirect steam vulcanization, the time to extend 1 to 2 times, generally used in the hollow core of the roller. For special rubber rollers that cannot be vulcanized with a vulcanizing tank, hot water is sometimes used for vulcanization, but the treatment of water pollution needs to be solved.

In order to prevent delamination between rubber roller and rubber core caused by different shrinkage due to thermal conductivity difference between rubber and metal core, the general vulcanization is mostly by slow heating and boosting, and the vulcanization time is much longer than the vulcanization time required for rubber itself. In order to achieve uniform vulcanization inside and outside of the large rubber roller and make the metal core and rubber thermal conductivity similar, the time spent in the tank is often as long as 24~48h, about 30~50 times the normal vulcanization time of rubber.

Most of the small and micro rubber rollers have now been changed to flat vulcanizer molding vulcanization, which has completely changed the traditional vulcanization method of rubber rollers. In recent years, the injection press molding, vacuum vulcanization, and can automatically open and close the mold, the degree of mechanization and automation is greatly improved, and the vulcanization time is short, the production efficiency is high, and the product quality is good. Especially when the rubber injection molding vulcanizer is used, the two processes of molding and vulcanization can be combined into one, and the time can be shortened to 2~4 min, which has become an important direction of the development of rubber roller production.

At present, the liquid rubber represented by polyurethane elastomer (PUR) has developed rapidly in the production of rubber rollers, and has opened up a new way of material and process revolution. It uses the form of pouring, the complex molding operation and heavy vulcanization equipment to get rid of, so that the roller production process is greatly simplified. However, the biggest problem is that the mold must be used. For large rubber rollers, especially for individual products, the production cost is greatly increased, which brings great difficulties to the promotion and use.

In order to solve this problem, in recent years, a new process of PUR rubber roller without mold manufacturing has begun to appear. It uses polyoxypropylene ether polyol (TDIOL), polytetrahydrofuran ether polyol (PIMG) and diphenylmethane diisocyanate (MDl) as raw materials. After mixing and stirring, it reacts quickly and quantitatively casts on the metal core of the slowly rotating rubber roller. Step by step, it realizes curing while pouring, and finally forms the rubber roller. This process is not only short process, high degree of mechanization and automation, but also saves the heavy mold, and can produce rubber rollers of various specifications and sizes according to the requirements, so that the cost is greatly reduced, and has become the main development direction of PUR rubber rollers.

In addition, in the world with liquid silicone rubber manufacturing office automation equipment used in the use of micro fine roller is also developing rapidly. They are divided into heating curing (LTV) and room temperature curing (RTV) two categories, the equipment used is also different from the above PUR, forming another type of casting form. Here, the most critical issue is how to control and reduce the viscosity of the compound to maintain a certain pressure and extrusion speed.

 

 

04

Surface treatment

 

Surface treatment is the last and most critical process in the production of rubber rollers, and the surface grinding state directly affects the performance of rubber rollers. At present, there are many kinds of grinding methods, but mainly mechanical turning and polishing. Therefore, grinding methods, grinding tools and abrasives used are very important. All enterprises regard them as technical know-how and maintain an attitude of non-publicity. The biggest problem is how to solve the grinding of rubber heating phenomenon and maintain the best surface after grinding deflection.

In addition to grinding the surface, the rubber roller should be thoroughly cleaned to remove the rubber powder attached to the surface. The higher requirements should be further polished on the surface, and some should be coated with resin coating, latex paint, magnetic powder, electrostatic powder, etc. At the same time, it can also be electroplated with a layer of required coating, or chemical oxidation treatment, etc., in order to achieve the purpose of light, corrosion resistance, magnetization and conductivity.

With the continuous development of the rubber roller, the coating technology on the surface of the rubber roller has also been rapidly improved, and the traditional method of coating rubber roller performance has begun to change. Specifically, the coating method is used to change and give new properties to the rubber roller. Such as the use of calender, scraping machine a kind of equipment, the addition of oil shielding layer to achieve the purpose of improving oil resistance, although the shape of the roller, the material is the same as the original, but its function has changed a lot, some into functional rollers, this surface treatment technology will be very promising in the future.

In summary, the rubber rollers used in production today have formed a product series with a unique process. Although the country is still dominated by traditional products, but the technical content is constantly improving, many products have entered the high-tech field, the added value is gradually increasing, is becoming another economic bright spot in industrial rubber products.
China's standards for rubber roller testing are mostly HG/T industry standards. There are only a few national standards that are more authoritative and representative. Compared with other national standards for plastic and rubber testing, they are not perfect. However, the ISO international standards for rubber rollers are of great reference value. Today, Xiao Bian sorted out the domestic and international rubber roller testing standards so that everyone can understand and check them.

 

Common domestic testing standards for rubber rollers

■ GB/T 23659-2017 Copier Cot
■ GB/T 21538-2008 Coated rolls for sheet metal
■ GB 9897-1988 Technical Conditions for Papermaking Rubber Rolls
■ HG/T 3954-2007 Metallurgical Cots
■ HG/T 3953-2007 Rubber roller for woodworking machinery
■ HG/T 2287-2008 printing roller
■ HG/T 2697-2017 Rubber Roller Part 2: Polyurethane Rubber Roller
■ HG/T 2013-2001 Cots Part 3: Fabric Pre-Shrinkable Rubber Blanket
■ HG/T 2447-2003 Cots Part 4: Printing and Dyeing Cots
■ HG/T 2446-2016 Rubber Rolls Part 5: Paper Making Rubber Rolls
■ HG/T 2445-2005 Cots Part 6: Cots for electronic typing (printing) machines
HG/T 2450-1999 Determination of apparent hardness of rubber rollers. International durometer method for rubber
■ HG/T 2644-2011 Technical Conditions for Rubber Roller Zhao Shi (P.J) Hardness Tester

 

International testing standards for rubber rollers

ISO 6123-1-2015 Rubber-or plastics-coated rollers-Specification-Part 1: Hardness requirements
■ ISO 6123-2-2015 Rubber-or plastics-coated rollers-Specification-Part 2: Surface characteristics
ISO 7267-1-2008 Rubber rollers-Determination of surface hardness-Part 1: International rubber hardness scale
ISO 7267-2-2008 Determination of surface hardness of rubber rollers-Part 2: Method for Shore hardness scale
ISO 7267-3-2011 Rubber rollers-Determination of surface hardness-Part 3: Percy-Jones method

Knowing the testing standards of rubber rollers, we naturally want to introduce the testing items of rubber rollers. As mentioned in the first paragraph of the article, the quality of the rubber roller is to be considered comprehensively, mainly from the hardness, physical properties, chemical properties, surface characteristics, other aspects of testing. Of course, the hardness belongs to the physical properties of the rubber roller. In addition, the rubber roller core is mentioned in most of the testing standards, so we can also be used as a reference index for rubber roller testing.

 

Main inspection items of rubber roller

1. Rubber roller hardness testing items: rubber international hardness, Zhao's hardness, Shore A hardness;
2. Test items for physical properties of rubber materials for rubber rollers: hardness, hardness tolerance, tensile strength, tensile elongation, flex cracking, tear strength, permanent compression performance, resilience, oil resistance quality change rate, Akron wear, vibration absorption and friction performance;
3. Test items for chemical properties of rubber materials for rubber rollers: liquid resistance, acid resistance test, alkali resistance test, hot air aging, corrosion resistance, electrical conductivity, heat transfer, hydrophilicity and solvent resistance;
4. Testing items of surface characteristics of rubber rollers: delamination, mechanical damage, impurities, bubbles, sand holes, surface roughness and surface treatment;
5. Other testing items of rubber roller: dimensional tolerance, thickness of rubber layer, adhesive strength between rubber layer and roller core;
6. Rubber roller core testing items: size, surface quality, wall thickness, balance, weld quality.

 

Common quality problems and repair defects

1. There are blisters, magazines, pores and depressions. The glue magazine is not filtered clean, and the thick gas cannot be discharged after the glue layer is overlapped.

For minor cases, the damaged part can be dug into a concave shape first, and the processing interface can be thickly coated with hot vulcanization adhesive and mixed rubber for high-temperature vulcanization molding, and then the belt can be cooled and polished by lathe. Serious rework to do again.
 

2. The surface treatment of the rubber and metal core delaminating roller core is not in place, the thread is too large and the specific surface area is small, the adhesive is not dried well, the adhesive is directly wrapped and vulcanized, the vulcanizing tank is raised too fast or the vulcanizing tank is short of sulfur. To remake.
 

3. The heavy skin rubber is unevenly remixed, and there are sundries on the rubber surface and the water cloth is not tightly wound. Hard rubber above 80 degrees is scrapped, and under 80 degrees Shore A, it can be turned and ground for 10mm thick new degreasing, coated with hot vulcanizing adhesive bonding tape, and wound and coated with rubber.
 

4. The vulcanization speed of the vulcanization design of the top glue and the bottom glue degumming is not coordinated, or the hard glue is caused by slow crosslinking.
 

5. If the partial shelling of the rubber roller is not serious and there is shelling at the slight edge, the damaged part and the undamaged part can be torn off on the lathe, and the glue and mixed rubber strip can be applied again to achieve the same hardness and be reused.